diff --git a/server/src/main/java/org/elasticsearch/action/RoutingMissingException.java b/server/src/main/java/org/elasticsearch/action/RoutingMissingException.java
index cb22248daa62e..5804598febd10 100644
--- a/server/src/main/java/org/elasticsearch/action/RoutingMissingException.java
+++ b/server/src/main/java/org/elasticsearch/action/RoutingMissingException.java
@@ -10,8 +10,10 @@
 package org.elasticsearch.action;
 
 import org.elasticsearch.ElasticsearchException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.rest.RestStatus;
 
 import java.io.IOException;
@@ -40,12 +42,18 @@ public RestStatus status() {
 
     public RoutingMissingException(StreamInput in) throws IOException {
         super(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readString();
+        }
         id = in.readString();
     }
 
     @Override
     protected void writeTo(StreamOutput out, Writer<Throwable> nestedExceptionsWriter) throws IOException {
         super.writeTo(out, nestedExceptionsWriter);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(id);
     }
 }
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexRequest.java
index fe2cdd482ae3d..84c040df758d3 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexRequest.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.admin.indices.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -112,6 +113,9 @@ public GetIndexRequest(TimeValue masterTimeout) {
     public GetIndexRequest(StreamInput in) throws IOException {
         super(in);
         indices = in.readStringArray();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readStringArray();
+        }
         indicesOptions = IndicesOptions.readIndicesOptions(in);
         features = in.readArray(i -> Feature.fromId(i.readByte()), Feature[]::new);
         humanReadable = in.readBoolean();
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexResponse.java
index 4a50f3b20a6c9..91f7dfd8a98f5 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexResponse.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.admin.indices.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.cluster.metadata.AliasMetadata;
 import org.elasticsearch.cluster.metadata.MappingMetadata;
@@ -19,6 +20,7 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.ChunkedToXContentObject;
 import org.elasticsearch.core.UpdateForV10;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.xcontent.ToXContent;
 
 import java.io.IOException;
@@ -75,10 +77,18 @@ public GetIndexResponse(
     @UpdateForV10(owner = UpdateForV10.Owner.DATA_MANAGEMENT)
     GetIndexResponse(StreamInput in) throws IOException {
         this.indices = in.readStringArray();
-        mappings = in.readImmutableOpenMap(
-            StreamInput::readString,
-            i -> i.readBoolean() ? new MappingMetadata(i) : MappingMetadata.EMPTY_MAPPINGS
-        );
+        mappings = in.readImmutableOpenMap(StreamInput::readString, in.getTransportVersion().before(TransportVersions.V_8_0_0) ? i -> {
+            int numMappings = i.readVInt();
+            assert numMappings == 0 || numMappings == 1 : "Expected 0 or 1 mappings but got " + numMappings;
+            if (numMappings == 1) {
+                String type = i.readString();
+                assert MapperService.SINGLE_MAPPING_NAME.equals(type) : "Expected [_doc] but got [" + type + "]";
+                return new MappingMetadata(i);
+            } else {
+                return MappingMetadata.EMPTY_MAPPINGS;
+            }
+        } : i -> i.readBoolean() ? new MappingMetadata(i) : MappingMetadata.EMPTY_MAPPINGS);
+
         aliases = in.readImmutableOpenMap(StreamInput::readString, i -> i.readCollectionAsList(AliasMetadata::new));
         settings = in.readImmutableOpenMap(StreamInput::readString, Settings::readSettingsFromStream);
         defaultSettings = in.readImmutableOpenMap(StreamInput::readString, Settings::readSettingsFromStream);
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsIndexRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsIndexRequest.java
index 829b9b8bde0b3..6ac78e7c27aed 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsIndexRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsIndexRequest.java
@@ -9,10 +9,12 @@
 
 package org.elasticsearch.action.admin.indices.mapping.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.OriginalIndices;
 import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.action.support.single.shard.SingleShardRequest;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 
@@ -27,8 +29,14 @@ public class GetFieldMappingsIndexRequest extends SingleShardRequest<GetFieldMap
 
     GetFieldMappingsIndexRequest(StreamInput in) throws IOException {
         super(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readStringArray();   // former types array
+        }
         fields = in.readStringArray();
         includeDefaults = in.readBoolean();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readBoolean();       // former probablySingleField boolean
+        }
         originalIndices = OriginalIndices.readOriginalIndices(in);
     }
 
@@ -66,8 +74,14 @@ public IndicesOptions indicesOptions() {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeStringArray(Strings.EMPTY_ARRAY);
+        }
         out.writeStringArray(fields);
         out.writeBoolean(includeDefaults);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeBoolean(false);
+        }
         OriginalIndices.writeOriginalIndices(originalIndices, out);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsRequest.java
index 423aa6e73bb31..1bab7267b108e 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsRequest.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.admin.indices.mapping.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.LegacyActionRequest;
@@ -18,6 +19,7 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 
 import java.io.IOException;
+import java.util.Arrays;
 
 /**
  * Request the mappings of specific fields
@@ -40,7 +42,18 @@ public GetFieldMappingsRequest() {}
     public GetFieldMappingsRequest(StreamInput in) throws IOException {
         super(in);
         indices = in.readStringArray();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            String[] types = in.readStringArray();
+            if (types != Strings.EMPTY_ARRAY) {
+                throw new IllegalArgumentException("Expected empty type array but received [" + Arrays.toString(types) + "]");
+            }
+
+        }
         indicesOptions = IndicesOptions.readIndicesOptions(in);
+        // Consume the deprecated local parameter
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readBoolean();
+        }
         fields = in.readStringArray();
         includeDefaults = in.readBoolean();
     }
@@ -104,7 +117,13 @@ public ActionRequestValidationException validate() {
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeStringArray(indices);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeStringArray(Strings.EMPTY_ARRAY);
+        }
         indicesOptions.writeIndicesOptions(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeBoolean(true);
+        }
         out.writeStringArray(fields);
         out.writeBoolean(includeDefaults);
     }
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java
index 78b29c87e9d89..9c0fe03e95748 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java
@@ -9,12 +9,14 @@
 
 package org.elasticsearch.action.admin.indices.mapping.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.index.mapper.Mapper;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.xcontent.ParseField;
 import org.elasticsearch.xcontent.ToXContentFragment;
 import org.elasticsearch.xcontent.ToXContentObject;
@@ -23,6 +25,7 @@
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.Collections;
 import java.util.Map;
 import java.util.Objects;
 
@@ -43,9 +46,17 @@ public class GetFieldMappingsResponse extends ActionResponse implements ToXConte
     }
 
     GetFieldMappingsResponse(StreamInput in) throws IOException {
-        mappings = in.readImmutableMap(
-            mapIn -> mapIn.readImmutableMap(inpt -> new FieldMappingMetadata(inpt.readString(), inpt.readBytesReference()))
-        );
+        mappings = in.readImmutableMap(mapIn -> {
+            if (mapIn.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                int typesSize = mapIn.readVInt();
+                assert typesSize == 1 || typesSize == 0 : "Expected 0 or 1 types but got " + typesSize;
+                if (typesSize == 0) {
+                    return Collections.emptyMap();
+                }
+                mapIn.readString(); // type
+            }
+            return mapIn.readImmutableMap(inpt -> new FieldMappingMetadata(inpt.readString(), inpt.readBytesReference()));
+        });
     }
 
     /** returns the retrieved field mapping. The return map keys are index, field (as specified in the request). */
@@ -123,6 +134,10 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeMap(mappings, (outpt, map) -> {
+            if (outpt.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                outpt.writeVInt(1);
+                outpt.writeString(MapperService.SINGLE_MAPPING_NAME);
+            }
             outpt.writeMap(map, (o, v) -> {
                 o.writeString(v.fullName());
                 o.writeBytesReference(v.source);
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsRequest.java
index e661c53c805a1..ca4314b4b9922 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsRequest.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.admin.indices.mapping.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -42,6 +43,9 @@ public GetMappingsRequest(TimeValue masterTimeout) {
     public GetMappingsRequest(StreamInput in) throws IOException {
         super(in);
         indices = in.readStringArray();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readStringArray();
+        }
         indicesOptions = IndicesOptions.readIndicesOptions(in);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java
index 72b2d951bc03e..05cc0d2cf05d8 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.action.admin.indices.mapping.put;
 
 import org.elasticsearch.ElasticsearchGenerationException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -23,6 +24,7 @@
 import org.elasticsearch.common.util.CollectionUtils;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.index.Index;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentFactory;
 import org.elasticsearch.xcontent.XContentType;
@@ -95,6 +97,12 @@ public PutMappingRequest(StreamInput in) throws IOException {
         super(in);
         indices = in.readStringArray();
         indicesOptions = IndicesOptions.readIndicesOptions(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            String type = in.readOptionalString();
+            if (MapperService.SINGLE_MAPPING_NAME.equals(type) == false) {
+                throw new IllegalArgumentException("Expected type [_doc] but received [" + type + "]");
+            }
+        }
         source = in.readString();
         concreteIndex = in.readOptionalWriteable(Index::new);
         origin = in.readOptionalString();
@@ -322,6 +330,9 @@ public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeStringArrayNullable(indices);
         indicesOptions.writeIndicesOptions(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(source);
         out.writeOptionalWriteable(concreteIndex);
         out.writeOptionalString(origin);
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/segments/IndicesSegmentsRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/segments/IndicesSegmentsRequest.java
index de9692cdaaded..bdacfb0ab642d 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/segments/IndicesSegmentsRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/segments/IndicesSegmentsRequest.java
@@ -31,6 +31,9 @@ public IndicesSegmentsRequest() {
 
     public IndicesSegmentsRequest(StreamInput in) throws IOException {
         super(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readBoolean();   // old 'verbose' option, since removed
+        }
         if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_15_0)) {
             this.includeVectorFormatsInfo = in.readBoolean();
         }
@@ -53,6 +56,9 @@ public boolean isIncludeVectorFormatsInfo() {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeBoolean(false);
+        }
         if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_15_0)) {
             out.writeBoolean(includeVectorFormatsInfo);
         }
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java
index 81b44b6720567..0f11cb45e08d5 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java
@@ -10,6 +10,7 @@
 
 import org.elasticsearch.ElasticsearchGenerationException;
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.admin.indices.alias.Alias;
@@ -76,7 +77,15 @@ public PutIndexTemplateRequest(StreamInput in) throws IOException {
         order = in.readInt();
         create = in.readBoolean();
         settings = readSettingsFromStream(in);
-        mappings = in.readOptionalString();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            int size = in.readVInt();
+            for (int i = 0; i < size; i++) {
+                in.readString();    // type - cannot assert on _doc because 7x allows arbitrary type names
+                this.mappings = in.readString();
+            }
+        } else {
+            this.mappings = in.readOptionalString();
+        }
         int aliasesSize = in.readVInt();
         for (int i = 0; i < aliasesSize; i++) {
             aliases.add(new Alias(in));
@@ -441,7 +450,15 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeInt(order);
         out.writeBoolean(create);
         settings.writeTo(out);
-        out.writeOptionalString(mappings);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeVInt(mappings == null ? 0 : 1);
+            if (mappings != null) {
+                out.writeString(MapperService.SINGLE_MAPPING_NAME);
+                out.writeString(mappings);
+            }
+        } else {
+            out.writeOptionalString(mappings);
+        }
         out.writeCollection(aliases);
         out.writeOptionalVInt(version);
     }
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ShardValidateQueryRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ShardValidateQueryRequest.java
index 0687b0fcbbed0..f41cb6fbc0306 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ShardValidateQueryRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ShardValidateQueryRequest.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.admin.indices.validate.query;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.support.broadcast.BroadcastShardRequest;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -33,6 +34,14 @@ public class ShardValidateQueryRequest extends BroadcastShardRequest {
     public ShardValidateQueryRequest(StreamInput in) throws IOException {
         super(in);
         query = in.readNamedWriteable(QueryBuilder.class);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            int typesSize = in.readVInt();
+            if (typesSize > 0) {
+                for (int i = 0; i < typesSize; i++) {
+                    in.readString();
+                }
+            }
+        }
         filteringAliases = AliasFilter.readFrom(in);
         explain = in.readBoolean();
         rewrite = in.readBoolean();
@@ -72,6 +81,9 @@ public long nowInMillis() {
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeNamedWriteable(query);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeVInt(0);   // no types to filter
+        }
         filteringAliases.writeTo(out);
         out.writeBoolean(explain);
         out.writeBoolean(rewrite);
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ValidateQueryRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ValidateQueryRequest.java
index 1117b1997b739..f30206c1d238a 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ValidateQueryRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/validate/query/ValidateQueryRequest.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.admin.indices.validate.query;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ValidateActions;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -48,6 +49,14 @@ public ValidateQueryRequest() {
     public ValidateQueryRequest(StreamInput in) throws IOException {
         super(in);
         query = in.readNamedWriteable(QueryBuilder.class);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            int typesSize = in.readVInt();
+            if (typesSize > 0) {
+                for (int i = 0; i < typesSize; i++) {
+                    in.readString();
+                }
+            }
+        }
         explain = in.readBoolean();
         rewrite = in.readBoolean();
         allShards = in.readBoolean();
@@ -129,6 +138,9 @@ public boolean allShards() {
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
         out.writeNamedWriteable(query);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeVInt(0);   // no types to filter
+        }
         out.writeBoolean(explain);
         out.writeBoolean(rewrite);
         out.writeBoolean(allShards);
diff --git a/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java b/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java
index 7b19c1928d535..349ae476dd724 100644
--- a/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java
+++ b/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.fieldcaps;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -46,8 +47,15 @@ public static IndexFieldCapabilities readFrom(StreamInput in) throws IOException
         boolean isMetadatafield = in.readBoolean();
         boolean isSearchable = in.readBoolean();
         boolean isAggregatable = in.readBoolean();
-        boolean isDimension = in.readBoolean();
-        TimeSeriesParams.MetricType metricType = in.readOptionalEnum(TimeSeriesParams.MetricType.class);
+        boolean isDimension;
+        TimeSeriesParams.MetricType metricType;
+        if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
+            isDimension = in.readBoolean();
+            metricType = in.readOptionalEnum(TimeSeriesParams.MetricType.class);
+        } else {
+            isDimension = false;
+            metricType = null;
+        }
         return new IndexFieldCapabilities(
             name,
             type,
@@ -67,8 +75,10 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeBoolean(isMetadatafield);
         out.writeBoolean(isSearchable);
         out.writeBoolean(isAggregatable);
-        out.writeBoolean(isDimension);
-        out.writeOptionalEnum(metricType);
+        if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
+            out.writeBoolean(isDimension);
+            out.writeOptionalEnum(metricType);
+        }
         out.writeMap(meta, StreamOutput::writeString);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/get/GetRequest.java b/server/src/main/java/org/elasticsearch/action/get/GetRequest.java
index aeb5f52094e94..5459782de9b5b 100644
--- a/server/src/main/java/org/elasticsearch/action/get/GetRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/get/GetRequest.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.action.get;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.RealtimeRequest;
 import org.elasticsearch.action.ValidateActions;
@@ -18,6 +19,7 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.lucene.uid.Versions;
 import org.elasticsearch.index.VersionType;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.SourceLoader;
 import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 
@@ -65,6 +67,9 @@ public GetRequest() {}
 
     public GetRequest(StreamInput in) throws IOException {
         super(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readString();
+        }
         id = in.readString();
         routing = in.readOptionalString();
         preference = in.readOptionalString();
@@ -81,6 +86,9 @@ public GetRequest(StreamInput in) throws IOException {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(id);
         out.writeOptionalString(routing);
         out.writeOptionalString(preference);
diff --git a/server/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java b/server/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java
index 98b52e7b7b83d..5e754f81055ab 100644
--- a/server/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.action.get;
 
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.CompositeIndicesRequest;
 import org.elasticsearch.action.IndicesRequest;
@@ -25,6 +26,7 @@
 import org.elasticsearch.common.lucene.uid.Versions;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.index.VersionType;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.SourceLoader;
 import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 import org.elasticsearch.xcontent.ParseField;
@@ -80,6 +82,9 @@ public Item() {
 
         public Item(StreamInput in) throws IOException {
             index = in.readString();
+            if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                in.readOptionalString();
+            }
             id = in.readString();
             routing = in.readOptionalString();
             storedFields = in.readOptionalStringArray();
@@ -171,6 +176,9 @@ public Item fetchSourceContext(FetchSourceContext fetchSourceContext) {
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             out.writeString(index);
+            if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                out.writeOptionalString(MapperService.SINGLE_MAPPING_NAME);
+            }
             out.writeString(id);
             out.writeOptionalString(routing);
             out.writeOptionalStringArray(storedFields);
diff --git a/server/src/main/java/org/elasticsearch/action/get/MultiGetResponse.java b/server/src/main/java/org/elasticsearch/action/get/MultiGetResponse.java
index 967762f9b2055..08db6dee8e543 100644
--- a/server/src/main/java/org/elasticsearch/action/get/MultiGetResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/get/MultiGetResponse.java
@@ -10,11 +10,13 @@
 package org.elasticsearch.action.get;
 
 import org.elasticsearch.ElasticsearchException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.xcontent.ParseField;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
@@ -45,6 +47,9 @@ public Failure(String index, String id, Exception exception) {
 
         Failure(StreamInput in) throws IOException {
             index = in.readString();
+            if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                in.readOptionalString();
+            }
             id = in.readString();
             exception = in.readException();
         }
@@ -73,6 +78,9 @@ public String getMessage() {
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             out.writeString(index);
+            if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                out.writeOptionalString(MapperService.SINGLE_MAPPING_NAME);
+            }
             out.writeString(id);
             out.writeException(exception);
         }
diff --git a/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java b/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
index 40078aa1efe81..f1b16d6099666 100644
--- a/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
@@ -37,6 +37,7 @@
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.VersionType;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.ingest.IngestService;
 import org.elasticsearch.xcontent.XContentBuilder;
@@ -159,6 +160,10 @@ public IndexRequest(StreamInput in) throws IOException {
 
     public IndexRequest(@Nullable ShardId shardId, StreamInput in) throws IOException {
         super(shardId, in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            String type = in.readOptionalString();
+            assert MapperService.SINGLE_MAPPING_NAME.equals(type) : "Expected [_doc] but received [" + type + "]";
+        }
         id = in.readOptionalString();
         routing = in.readOptionalString();
         boolean beforeSourceContext = in.getTransportVersion().supports(INDEX_SOURCE) == false;
@@ -745,6 +750,9 @@ public void writeThin(StreamOutput out) throws IOException {
     }
 
     private void writeBody(StreamOutput out) throws IOException {
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeOptionalString(id);
         out.writeOptionalString(routing);
         if (out.getTransportVersion().supports(INDEX_SOURCE)) {
diff --git a/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java b/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java
index 6e77aadc5448b..f3e7eacaeb9df 100644
--- a/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.action.search;
 
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
@@ -243,6 +244,15 @@ public SearchRequest(StreamInput in) throws IOException {
         preference = in.readOptionalString();
         scrollKeepAlive = in.readOptionalTimeValue();
         source = in.readOptionalWriteable(SearchSourceBuilder::new);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types no longer relevant so ignore
+            String[] types = in.readStringArray();
+            if (types.length > 0) {
+                throw new IllegalStateException(
+                    "types are no longer supported in search requests but found [" + Arrays.toString(types) + "]"
+                );
+            }
+        }
         indicesOptions = IndicesOptions.readIndicesOptions(in);
         requestCache = in.readOptionalBoolean();
         batchedReduceSize = in.readVInt();
@@ -282,6 +292,10 @@ public void writeTo(StreamOutput out, boolean skipIndices) throws IOException {
         out.writeOptionalString(preference);
         out.writeOptionalTimeValue(scrollKeepAlive);
         out.writeOptionalWriteable(source);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types not supported so send an empty array to previous versions
+            out.writeStringArray(Strings.EMPTY_ARRAY);
+        }
         indicesOptions.writeIndicesOptions(out);
         out.writeOptionalBoolean(requestCache);
         out.writeVInt(batchedReduceSize);
diff --git a/server/src/main/java/org/elasticsearch/action/termvectors/MultiTermVectorsResponse.java b/server/src/main/java/org/elasticsearch/action/termvectors/MultiTermVectorsResponse.java
index 23996ec4976e6..42196fac28528 100644
--- a/server/src/main/java/org/elasticsearch/action/termvectors/MultiTermVectorsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/termvectors/MultiTermVectorsResponse.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.action.termvectors;
 
 import org.elasticsearch.ElasticsearchException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.collect.Iterators;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -39,6 +40,13 @@ public Failure(String index, String id, Exception cause) {
 
         public Failure(StreamInput in) throws IOException {
             index = in.readString();
+            if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                // types no longer relevant so ignore
+                String type = in.readOptionalString();
+                if (type != null) {
+                    throw new IllegalStateException("types are no longer supported but found [" + type + "]");
+                }
+            }
             id = in.readString();
             cause = in.readException();
         }
@@ -67,6 +75,10 @@ public Exception getCause() {
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             out.writeString(index);
+            if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                // types not supported so send an empty array to previous versions
+                out.writeOptionalString(null);
+            }
             out.writeString(id);
             out.writeException(cause);
         }
diff --git a/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsRequest.java b/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsRequest.java
index 0e410969cc639..7a7b2afab75d1 100644
--- a/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsRequest.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.action.termvectors;
 
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.RealtimeRequest;
 import org.elasticsearch.action.ValidateActions;
@@ -124,6 +125,10 @@ public TermVectorsRequest() {}
 
     TermVectorsRequest(StreamInput in) throws IOException {
         super(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types no longer relevant so ignore
+            in.readString();
+        }
         id = in.readString();
 
         if (in.readBoolean()) {
@@ -469,6 +474,10 @@ public ActionRequestValidationException validate() {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         super.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types not supported so send an empty array to previous versions
+            out.writeString("_doc");
+        }
         out.writeString(id);
 
         out.writeBoolean(doc != null);
diff --git a/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsResponse.java b/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsResponse.java
index 1e5e0397ff957..4c4aa7de46f6b 100644
--- a/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsResponse.java
@@ -17,6 +17,7 @@
 import org.apache.lucene.util.ArrayUtil;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.CharsRefBuilder;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.termvectors.TermVectorsRequest.Flag;
 import org.elasticsearch.common.bytes.BytesArray;
@@ -25,6 +26,7 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
 
@@ -85,6 +87,10 @@ public TermVectorsResponse(String index, String id) {
 
     TermVectorsResponse(StreamInput in) throws IOException {
         index = in.readString();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types no longer relevant so ignore
+            in.readString();
+        }
         id = in.readString();
         docVersion = in.readVLong();
         exists = in.readBoolean();
@@ -99,6 +105,10 @@ public TermVectorsResponse(String index, String id) {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(index);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types not supported so send an empty array to previous versions
+            out.writeString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(id);
         out.writeVLong(docVersion);
         final boolean docExists = isExists();
diff --git a/server/src/main/java/org/elasticsearch/action/update/UpdateRequest.java b/server/src/main/java/org/elasticsearch/action/update/UpdateRequest.java
index 079b6611119b2..657ad029626af 100644
--- a/server/src/main/java/org/elasticsearch/action/update/UpdateRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/update/UpdateRequest.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.action.update;
 
 import org.apache.lucene.util.RamUsageEstimator;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.DocWriteRequest;
 import org.elasticsearch.action.index.IndexRequest;
@@ -27,6 +28,7 @@
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.index.VersionType;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.script.Script;
 import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
@@ -133,6 +135,10 @@ public UpdateRequest(StreamInput in) throws IOException {
     public UpdateRequest(@Nullable ShardId shardId, StreamInput in) throws IOException {
         super(shardId, in);
         waitForActiveShards = ActiveShardCount.readFrom(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            String type = in.readString();
+            assert MapperService.SINGLE_MAPPING_NAME.equals(type) : "Expected [_doc] but received [" + type + "]";
+        }
         id = in.readString();
         routing = in.readOptionalString();
         if (in.readBoolean()) {
@@ -701,6 +707,9 @@ public void writeThin(StreamOutput out) throws IOException {
 
     private void doWrite(StreamOutput out, boolean thin) throws IOException {
         waitForActiveShards.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(id);
         out.writeOptionalString(routing);
 
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/MappingMetadata.java b/server/src/main/java/org/elasticsearch/cluster/metadata/MappingMetadata.java
index 1b3dbcc9a50e9..ee4869508eaf2 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/MappingMetadata.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/MappingMetadata.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.cluster.metadata;
 
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.cluster.Diff;
 import org.elasticsearch.cluster.SimpleDiffable;
 import org.elasticsearch.common.compress.CompressedXContent;
@@ -75,7 +76,13 @@ public MappingMetadata(String type, Map<String, Object> mapping) {
     }
 
     public static void writeMappingMetadata(StreamOutput out, Map<String, MappingMetadata> mappings) throws IOException {
-        out.writeMap(mappings, (o, v) -> {
+        out.writeMap(mappings, out.getTransportVersion().before(TransportVersions.V_8_0_0) ? (o, v) -> {
+            o.writeVInt(v == EMPTY_MAPPINGS ? 0 : 1);
+            if (v != EMPTY_MAPPINGS) {
+                o.writeString(MapperService.SINGLE_MAPPING_NAME);
+                v.writeTo(o);
+            }
+        } : (o, v) -> {
             o.writeBoolean(v != EMPTY_MAPPINGS);
             if (v != EMPTY_MAPPINGS) {
                 v.writeTo(o);
diff --git a/server/src/main/java/org/elasticsearch/common/xcontent/XContentHelper.java b/server/src/main/java/org/elasticsearch/common/xcontent/XContentHelper.java
index 0215fb1e97686..f62fa6abff3a7 100644
--- a/server/src/main/java/org/elasticsearch/common/xcontent/XContentHelper.java
+++ b/server/src/main/java/org/elasticsearch/common/xcontent/XContentHelper.java
@@ -11,6 +11,7 @@
 
 import org.elasticsearch.ElasticsearchGenerationException;
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
@@ -743,7 +744,12 @@ public static BytesReference childBytes(XContentParser parser) throws IOExceptio
      * @param xContentType an instance to serialize
      */
     public static void writeTo(StreamOutput out, XContentType xContentType) throws IOException {
-        out.writeVInt(xContentType.ordinal());
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // when sending an enumeration to <v8 node it does not have new VND_ XContentType instances
+            out.writeVInt(xContentType.canonical().ordinal());
+        } else {
+            out.writeVInt(xContentType.ordinal());
+        }
     }
 
     /**
diff --git a/server/src/main/java/org/elasticsearch/gateway/LocalAllocateDangledIndices.java b/server/src/main/java/org/elasticsearch/gateway/LocalAllocateDangledIndices.java
index d0c8425a0b128..0727ad1bade7f 100644
--- a/server/src/main/java/org/elasticsearch/gateway/LocalAllocateDangledIndices.java
+++ b/server/src/main/java/org/elasticsearch/gateway/LocalAllocateDangledIndices.java
@@ -11,6 +11,7 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.ActionListenerResponseHandler;
 import org.elasticsearch.action.support.ChannelActionListener;
@@ -276,11 +277,19 @@ public void writeTo(StreamOutput out) throws IOException {
 
     public static class AllocateDangledResponse extends TransportResponse {
 
-        private AllocateDangledResponse(StreamInput in) throws IOException {}
+        private AllocateDangledResponse(StreamInput in) throws IOException {
+            if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                in.readBoolean();
+            }
+        }
 
         private AllocateDangledResponse() {}
 
         @Override
-        public void writeTo(StreamOutput out) throws IOException {}
+        public void writeTo(StreamOutput out) throws IOException {
+            if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                out.writeBoolean(true);
+            }
+        }
     }
 }
diff --git a/server/src/main/java/org/elasticsearch/index/engine/Segment.java b/server/src/main/java/org/elasticsearch/index/engine/Segment.java
index c91f87fc96df3..f31fbd3f6af50 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/Segment.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/Segment.java
@@ -15,6 +15,7 @@
 import org.apache.lucene.search.SortedNumericSortField;
 import org.apache.lucene.search.SortedSetSelector;
 import org.apache.lucene.search.SortedSetSortField;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -52,6 +53,9 @@ public Segment(StreamInput in) throws IOException {
         version = Lucene.parseVersionLenient(in.readOptionalString(), null);
         compound = in.readOptionalBoolean();
         mergeId = in.readOptionalString();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readLong(); // memoryInBytes
+        }
         if (in.readBoolean()) {
             readRamTree(in);
         }
@@ -156,6 +160,10 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeOptionalString(version.toString());
         out.writeOptionalBoolean(compound);
         out.writeOptionalString(mergeId);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeLong(0); // memoryInBytes
+        }
+
         out.writeBoolean(false);
         writeSegmentSort(out, segmentSort);
         boolean hasAttributes = attributes != null;
diff --git a/server/src/main/java/org/elasticsearch/index/engine/SegmentsStats.java b/server/src/main/java/org/elasticsearch/index/engine/SegmentsStats.java
index dda5d5116fb60..d54f21193afe6 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/SegmentsStats.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/SegmentsStats.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.index.engine;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -39,6 +40,15 @@ public SegmentsStats() {
 
     public SegmentsStats(StreamInput in) throws IOException {
         count = in.readVLong();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readLong(); // memoryInBytes
+            in.readLong(); // termsMemoryInBytes
+            in.readLong(); // storedFieldsMemoryInBytes
+            in.readLong(); // termVectorsMemoryInBytes
+            in.readLong(); // normsMemoryInBytes
+            in.readLong(); // pointsMemoryInBytes
+            in.readLong(); // docValuesMemoryInBytes
+        }
         indexWriterMemoryInBytes = in.readLong();
         versionMapMemoryInBytes = in.readLong();
         bitsetMemoryInBytes = in.readLong();
@@ -211,6 +221,15 @@ static final class Fields {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeVLong(count);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeLong(0L); // memoryInBytes
+            out.writeLong(0L); // termsMemoryInBytes
+            out.writeLong(0L); // storedFieldsMemoryInBytes
+            out.writeLong(0L); // termVectorsMemoryInBytes
+            out.writeLong(0L); // normsMemoryInBytes
+            out.writeLong(0L); // pointsMemoryInBytes
+            out.writeLong(0L); // docValuesMemoryInBytes
+        }
         out.writeLong(indexWriterMemoryInBytes);
         out.writeLong(versionMapMemoryInBytes);
         out.writeLong(bitsetMemoryInBytes);
diff --git a/server/src/main/java/org/elasticsearch/index/get/GetResult.java b/server/src/main/java/org/elasticsearch/index/get/GetResult.java
index b1dac63c9b8cf..b8c842eefb836 100644
--- a/server/src/main/java/org/elasticsearch/index/get/GetResult.java
+++ b/server/src/main/java/org/elasticsearch/index/get/GetResult.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.index.get;
 
 import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.compress.CompressorFactory;
@@ -20,6 +21,7 @@
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.index.mapper.IgnoredFieldMapper;
 import org.elasticsearch.index.mapper.IgnoredSourceFieldMapper;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.SourceFieldMapper;
 import org.elasticsearch.search.lookup.Source;
 import org.elasticsearch.xcontent.ToXContentObject;
@@ -59,6 +61,9 @@ public class GetResult implements Writeable, Iterable<DocumentField>, ToXContent
 
     public GetResult(StreamInput in) throws IOException {
         index = in.readString();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readOptionalString();
+        }
         id = in.readString();
         seqNo = in.readZLong();
         primaryTerm = in.readVLong();
@@ -282,6 +287,9 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(index);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(id);
         out.writeZLong(seqNo);
         out.writeVLong(primaryTerm);
diff --git a/server/src/main/java/org/elasticsearch/index/query/IdsQueryBuilder.java b/server/src/main/java/org/elasticsearch/index/query/IdsQueryBuilder.java
index bb60f31f23e12..fbb905b702293 100644
--- a/server/src/main/java/org/elasticsearch/index/query/IdsQueryBuilder.java
+++ b/server/src/main/java/org/elasticsearch/index/query/IdsQueryBuilder.java
@@ -11,7 +11,9 @@
 
 import org.apache.lucene.search.Query;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.ParsingException;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.index.mapper.IdFieldMapper;
@@ -23,6 +25,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Objects;
@@ -52,11 +55,22 @@ public IdsQueryBuilder() {
      */
     public IdsQueryBuilder(StreamInput in) throws IOException {
         super(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types no longer relevant so ignore
+            String[] types = in.readStringArray();
+            if (types.length > 0) {
+                throw new IllegalStateException("types are no longer supported in ids query but found [" + Arrays.toString(types) + "]");
+            }
+        }
         Collections.addAll(ids, in.readStringArray());
     }
 
     @Override
     protected void doWriteTo(StreamOutput out) throws IOException {
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types not supported so send an empty array to previous versions
+            out.writeStringArray(Strings.EMPTY_ARRAY);
+        }
         out.writeStringCollection(ids);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/index/query/MatchQueryBuilder.java b/server/src/main/java/org/elasticsearch/index/query/MatchQueryBuilder.java
index a1f4e14949acd..56e002287e1e3 100644
--- a/server/src/main/java/org/elasticsearch/index/query/MatchQueryBuilder.java
+++ b/server/src/main/java/org/elasticsearch/index/query/MatchQueryBuilder.java
@@ -13,6 +13,7 @@
 import org.apache.lucene.search.FuzzyQuery;
 import org.apache.lucene.search.Query;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -112,6 +113,10 @@ public MatchQueryBuilder(StreamInput in) throws IOException {
         minimumShouldMatch = in.readOptionalString();
         fuzzyRewrite = in.readOptionalString();
         fuzziness = in.readOptionalWriteable(Fuzziness::new);
+        // cutoff_frequency has been removed
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readOptionalFloat();
+        }
         autoGenerateSynonymsPhraseQuery = in.readBoolean();
     }
 
@@ -130,6 +135,10 @@ protected void doWriteTo(StreamOutput out) throws IOException {
         out.writeOptionalString(minimumShouldMatch);
         out.writeOptionalString(fuzzyRewrite);
         out.writeOptionalWriteable(fuzziness);
+        // cutoff_frequency has been removed
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalFloat(null);
+        }
         out.writeBoolean(autoGenerateSynonymsPhraseQuery);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/index/query/MoreLikeThisQueryBuilder.java b/server/src/main/java/org/elasticsearch/index/query/MoreLikeThisQueryBuilder.java
index a8a3858aabf38..4b2f4f2517622 100644
--- a/server/src/main/java/org/elasticsearch/index/query/MoreLikeThisQueryBuilder.java
+++ b/server/src/main/java/org/elasticsearch/index/query/MoreLikeThisQueryBuilder.java
@@ -17,6 +17,7 @@
 import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.RoutingMissingException;
 import org.elasticsearch.action.termvectors.MultiTermVectorsItemResponse;
 import org.elasticsearch.action.termvectors.MultiTermVectorsRequest;
@@ -200,6 +201,13 @@ public Item(@Nullable String index, XContentBuilder doc) {
         @SuppressWarnings("unchecked")
         Item(StreamInput in) throws IOException {
             index = in.readOptionalString();
+            if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                // types no longer relevant so ignore
+                String type = in.readOptionalString();
+                if (type != null) {
+                    throw new IllegalStateException("types are no longer supported but found [" + type + "]");
+                }
+            }
             if (in.readBoolean()) {
                 doc = (BytesReference) in.readGenericValue();
                 xContentType = in.readEnum(XContentType.class);
@@ -216,6 +224,10 @@ public Item(@Nullable String index, XContentBuilder doc) {
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             out.writeOptionalString(index);
+            if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+                // types not supported so send an empty array to previous versions
+                out.writeOptionalString(null);
+            }
             out.writeBoolean(doc != null);
             if (doc != null) {
                 out.writeGenericValue(doc);
diff --git a/server/src/main/java/org/elasticsearch/index/query/MultiMatchQueryBuilder.java b/server/src/main/java/org/elasticsearch/index/query/MultiMatchQueryBuilder.java
index db072d93cd66a..df7f28a7a15d5 100644
--- a/server/src/main/java/org/elasticsearch/index/query/MultiMatchQueryBuilder.java
+++ b/server/src/main/java/org/elasticsearch/index/query/MultiMatchQueryBuilder.java
@@ -13,6 +13,7 @@
 import org.apache.lucene.search.Query;
 import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -221,6 +222,9 @@ public MultiMatchQueryBuilder(StreamInput in) throws IOException {
         fuzzyRewrite = in.readOptionalString();
         tieBreaker = in.readOptionalFloat();
         lenient = in.readOptionalBoolean();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readOptionalFloat();
+        }
         zeroTermsQuery = ZeroTermsQueryOption.readFromStream(in);
         autoGenerateSynonymsPhraseQuery = in.readBoolean();
         fuzzyTranspositions = in.readBoolean();
@@ -241,6 +245,9 @@ protected void doWriteTo(StreamOutput out) throws IOException {
         out.writeOptionalString(fuzzyRewrite);
         out.writeOptionalFloat(tieBreaker);
         out.writeOptionalBoolean(lenient);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalFloat(null);
+        }
         zeroTermsQuery.writeTo(out);
         out.writeBoolean(autoGenerateSynonymsPhraseQuery);
         out.writeBoolean(fuzzyTranspositions);
diff --git a/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java b/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java
index 0f60518e90256..f9ac1e9cb5b86 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java
@@ -10,15 +10,18 @@
 package org.elasticsearch.index.shard;
 
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.xcontent.ToXContent;
 import org.elasticsearch.xcontent.ToXContentFragment;
 import org.elasticsearch.xcontent.XContentBuilder;
 
 import java.io.IOException;
+import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
 
@@ -394,6 +397,13 @@ public IndexingStats() {
 
     public IndexingStats(StreamInput in) throws IOException {
         totalStats = new Stats(in);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            if (in.readBoolean()) {
+                Map<String, Stats> typeStats = in.readMap(Stats::new);
+                assert typeStats.size() == 1;
+                assert typeStats.containsKey(MapperService.SINGLE_MAPPING_NAME);
+            }
+        }
     }
 
     public IndexingStats(Stats totalStats) {
@@ -463,5 +473,8 @@ static final class Fields {
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         totalStats.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeBoolean(false);
+        }
     }
 }
diff --git a/server/src/main/java/org/elasticsearch/index/translog/Translog.java b/server/src/main/java/org/elasticsearch/index/translog/Translog.java
index b2b1edfd7e92c..a5088b5896c80 100644
--- a/server/src/main/java/org/elasticsearch/index/translog/Translog.java
+++ b/server/src/main/java/org/elasticsearch/index/translog/Translog.java
@@ -1370,9 +1370,9 @@ protected void writeHeader(int format, StreamOutput out) throws IOException {
 
         @Override
         public void writeBody(final StreamOutput out) throws IOException {
-            final int format = out.getTransportVersion().supports(REORDERED_TRANSLOG_OPERATIONS)
-                ? SERIALIZATION_FORMAT
-                : FORMAT_NO_DOC_TYPE;
+            final int format = out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)
+                ? out.getTransportVersion().supports(REORDERED_TRANSLOG_OPERATIONS) ? SERIALIZATION_FORMAT : FORMAT_NO_DOC_TYPE
+                : FORMAT_NO_VERSION_TYPE;
             if (format < FORMAT_REORDERED) {
                 out.writeVInt(format);
                 out.writeString(Uid.decodeId(uid.bytes, uid.offset, uid.length));
@@ -1572,9 +1572,9 @@ public long version() {
 
         @Override
         public void writeBody(final StreamOutput out) throws IOException {
-            final int format = out.getTransportVersion().supports(REORDERED_TRANSLOG_OPERATIONS)
-                ? SERIALIZATION_FORMAT
-                : FORMAT_NO_DOC_TYPE;
+            final int format = out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)
+                ? out.getTransportVersion().supports(REORDERED_TRANSLOG_OPERATIONS) ? SERIALIZATION_FORMAT : FORMAT_NO_DOC_TYPE
+                : FORMAT_NO_VERSION_TYPE;
             if (format < FORMAT_REORDERED) {
                 out.writeVInt(format);
                 if (format < FORMAT_NO_DOC_TYPE) {
diff --git a/server/src/main/java/org/elasticsearch/indices/TermsLookup.java b/server/src/main/java/org/elasticsearch/indices/TermsLookup.java
index 75cbed396565b..0bab521a984e2 100644
--- a/server/src/main/java/org/elasticsearch/indices/TermsLookup.java
+++ b/server/src/main/java/org/elasticsearch/indices/TermsLookup.java
@@ -9,9 +9,11 @@
 
 package org.elasticsearch.indices;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.query.TermsQueryBuilder;
 import org.elasticsearch.xcontent.ConstructingObjectParser;
 import org.elasticsearch.xcontent.ParseField;
@@ -53,6 +55,9 @@ public TermsLookup(String index, String id, String path) {
      * Read from a stream.
      */
     public TermsLookup(StreamInput in) throws IOException {
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readOptionalString();
+        }
         id = in.readString();
         path = in.readString();
         index = in.readString();
@@ -61,6 +66,9 @@ public TermsLookup(StreamInput in) throws IOException {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalString(MapperService.SINGLE_MAPPING_NAME);
+        }
         out.writeString(id);
         out.writeString(path);
         out.writeString(index);
diff --git a/server/src/main/java/org/elasticsearch/monitor/os/OsStats.java b/server/src/main/java/org/elasticsearch/monitor/os/OsStats.java
index 715e5851e9c28..840ea14364f96 100644
--- a/server/src/main/java/org/elasticsearch/monitor/os/OsStats.java
+++ b/server/src/main/java/org/elasticsearch/monitor/os/OsStats.java
@@ -12,6 +12,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -294,13 +295,17 @@ public Mem(StreamInput in) throws IOException {
                 total = 0;
             }
             this.total = total;
-            long adjustedTotal = in.readLong();
-            assert adjustedTotal >= 0 : "expected adjusted total memory to be positive, got: " + adjustedTotal;
-            if (adjustedTotal < 0) {
-                logger.error("negative adjusted total memory [{}] deserialized in memory stats", adjustedTotal);
-                adjustedTotal = 0;
+            if (in.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
+                long adjustedTotal = in.readLong();
+                assert adjustedTotal >= 0 : "expected adjusted total memory to be positive, got: " + adjustedTotal;
+                if (adjustedTotal < 0) {
+                    logger.error("negative adjusted total memory [{}] deserialized in memory stats", adjustedTotal);
+                    adjustedTotal = 0;
+                }
+                this.adjustedTotal = adjustedTotal;
+            } else {
+                this.adjustedTotal = total;
             }
-            this.adjustedTotal = adjustedTotal;
             long free = in.readLong();
             assert free >= 0 : "expected free memory to be positive, got: " + free;
             if (free < 0) {
@@ -313,7 +318,9 @@ public Mem(StreamInput in) throws IOException {
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             out.writeLong(total);
-            out.writeLong(adjustedTotal);
+            if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
+                out.writeLong(adjustedTotal);
+            }
             out.writeLong(free);
         }
 
diff --git a/server/src/main/java/org/elasticsearch/script/ScriptContextStats.java b/server/src/main/java/org/elasticsearch/script/ScriptContextStats.java
index e726b63bfcd31..5e070690b97ee 100644
--- a/server/src/main/java/org/elasticsearch/script/ScriptContextStats.java
+++ b/server/src/main/java/org/elasticsearch/script/ScriptContextStats.java
@@ -9,6 +9,7 @@
 
 package org.elasticsearch.script;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -58,8 +59,10 @@ public static ScriptContextStats read(StreamInput in) throws IOException {
         var compilations = in.readVLong();
         var cacheEvictions = in.readVLong();
         var compilationLimitTriggered = in.readVLong();
-        TimeSeries compilationsHistory = new TimeSeries(in);
-        TimeSeries cacheEvictionsHistory = new TimeSeries(in);
+        TimeSeries compilationsHistory;
+        TimeSeries cacheEvictionsHistory;
+        compilationsHistory = new TimeSeries(in);
+        cacheEvictionsHistory = new TimeSeries(in);
         return new ScriptContextStats(
             context,
             compilations,
@@ -88,8 +91,10 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeVLong(compilations);
         out.writeVLong(cacheEvictions);
         out.writeVLong(compilationLimitTriggered);
-        compilationsHistory.writeTo(out);
-        cacheEvictionsHistory.writeTo(out);
+        if (out.getTransportVersion().onOrAfter(TransportVersions.V_8_0_0)) {
+            compilationsHistory.writeTo(out);
+            cacheEvictionsHistory.writeTo(out);
+        }
     }
 
     public String getContext() {
diff --git a/server/src/main/java/org/elasticsearch/search/SearchHit.java b/server/src/main/java/org/elasticsearch/search/SearchHit.java
index b381b828ca8d7..31429dd91d9a9 100644
--- a/server/src/main/java/org/elasticsearch/search/SearchHit.java
+++ b/server/src/main/java/org/elasticsearch/search/SearchHit.java
@@ -204,6 +204,9 @@ public static SearchHit readFrom(StreamInput in, boolean pooled) throws IOExcept
             rank = NO_RANK;
         }
         final Text id = in.readOptionalText();
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            in.readOptionalText();
+        }
         final NestedIdentity nestedIdentity = in.readOptionalWriteable(NestedIdentity::new);
         final long version = in.readLong();
         final long seqNo = in.readZLong();
@@ -315,6 +318,9 @@ public void writeTo(StreamOutput out) throws IOException {
             throw new IllegalArgumentException("cannot serialize [rank] to version [" + out.getTransportVersion().toReleaseVersion() + "]");
         }
         out.writeOptionalText(id);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalText(SINGLE_MAPPING_TYPE);
+        }
         out.writeOptionalWriteable(nestedIdentity);
         out.writeLong(version);
         out.writeZLong(seqNo);
diff --git a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java
index d7c788c9a3533..26da58334e16b 100644
--- a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java
+++ b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalBinaryRange.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.search.aggregations.bucket.range;
 
 import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.core.Releasables;
@@ -58,7 +59,9 @@ private static String generateKey(BytesRef from, BytesRef to, DocValueFormat for
         }
 
         private static Bucket createFromStream(StreamInput in, DocValueFormat format) throws IOException {
-            String key = in.readOptionalString();
+            // NOTE: the key is required in version == 8.0.0,
+            // while it is optional for all subsequent versions.
+            String key = in.getTransportVersion().equals(TransportVersions.V_8_0_0) ? in.readString() : in.readOptionalString();
             BytesRef from = in.readOptional(StreamInput::readBytesRef);
             BytesRef to = in.readOptional(StreamInput::readBytesRef);
             long docCount = in.readLong();
@@ -69,7 +72,11 @@ private static Bucket createFromStream(StreamInput in, DocValueFormat format) th
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            out.writeOptionalString(key);
+            if (out.getTransportVersion().equals(TransportVersions.V_8_0_0)) {
+                out.writeString(key == null ? generateKey(from, to, format) : key);
+            } else {
+                out.writeOptionalString(key);
+            }
             out.writeOptional(StreamOutput::writeBytesRef, from);
             out.writeOptional(StreamOutput::writeBytesRef, to);
             out.writeLong(docCount);
diff --git a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java
index 01076668674e5..b0ddc3e47354d 100644
--- a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java
+++ b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/range/InternalRange.java
@@ -8,6 +8,7 @@
  */
 package org.elasticsearch.search.aggregations.bucket.range;
 
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.core.Releasables;
@@ -137,7 +138,13 @@ private static String generateKey(double from, double to, DocValueFormat format)
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
-            out.writeOptionalString(key);
+            // NOTE: the key is required in version == 8.0.0,
+            // while it is optional for all subsequent versions.
+            if (out.getTransportVersion().equals(TransportVersions.V_8_0_0)) {
+                out.writeString(key == null ? generateKey(from, to, format) : key);
+            } else {
+                out.writeOptionalString(key);
+            }
             out.writeDouble(from);
             out.writeOptionalDouble(from);
             out.writeDouble(to);
@@ -223,7 +230,9 @@ public InternalRange(StreamInput in) throws IOException {
         int size = in.readVInt();
         List<B> ranges = new ArrayList<>(size);
         for (int i = 0; i < size; i++) {
-            final String key = in.readOptionalString();
+            // NOTE: the key is required in version == 8.0.0,
+            // while it is optional for all subsequent versions.
+            final String key = in.getTransportVersion().equals(TransportVersions.V_8_0_0) ? in.readString() : in.readOptionalString();
             double from = in.readDouble();
             final Double originalFrom = in.readOptionalDouble();
             if (originalFrom != null) {
diff --git a/server/src/main/java/org/elasticsearch/search/internal/ShardSearchRequest.java b/server/src/main/java/org/elasticsearch/search/internal/ShardSearchRequest.java
index 0bdfb6187d142..32ac446b85fdc 100644
--- a/server/src/main/java/org/elasticsearch/search/internal/ShardSearchRequest.java
+++ b/server/src/main/java/org/elasticsearch/search/internal/ShardSearchRequest.java
@@ -20,6 +20,7 @@
 import org.elasticsearch.cluster.metadata.AliasMetadata;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
 import org.elasticsearch.common.CheckedBiConsumer;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.hash.MessageDigests;
@@ -54,6 +55,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
@@ -304,6 +306,15 @@ public ShardSearchRequest(StreamInput in) throws IOException {
                 source.subSearches(subSearchSourceBuilders);
             }
         }
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types no longer relevant so ignore
+            String[] types = in.readStringArray();
+            if (types.length > 0) {
+                throw new IllegalStateException(
+                    "types are no longer supported in search requests but found [" + Arrays.toString(types) + "]"
+                );
+            }
+        }
         aliasFilter = AliasFilter.readFrom(in);
         indexBoost = in.readFloat();
         nowInMillis = in.readVLong();
@@ -351,6 +362,10 @@ protected final void innerWriteTo(StreamOutput out, boolean asKey) throws IOExce
             }
             out.writeNamedWriteableCollection(rankQueryBuilders);
         }
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            // types not supported so send an empty array to previous versions
+            out.writeStringArray(Strings.EMPTY_ARRAY);
+        }
         aliasFilter.writeTo(out);
         out.writeFloat(indexBoost);
         if (asKey == false) {
diff --git a/server/src/main/java/org/elasticsearch/search/sort/GeoDistanceSortBuilder.java b/server/src/main/java/org/elasticsearch/search/sort/GeoDistanceSortBuilder.java
index 422a99e7d72f5..d703eaed1dc95 100644
--- a/server/src/main/java/org/elasticsearch/search/sort/GeoDistanceSortBuilder.java
+++ b/server/src/main/java/org/elasticsearch/search/sort/GeoDistanceSortBuilder.java
@@ -21,6 +21,7 @@
 import org.apache.lucene.util.BitSet;
 import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.ParsingException;
 import org.elasticsearch.common.geo.GeoDistance;
 import org.elasticsearch.common.geo.GeoPoint;
@@ -39,6 +40,7 @@
 import org.elasticsearch.index.fielddata.plain.LatLonPointIndexFieldData;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.query.GeoValidationMethod;
+import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.index.query.QueryRewriteContext;
 import org.elasticsearch.index.query.SearchExecutionContext;
 import org.elasticsearch.search.DocValueFormat;
@@ -161,6 +163,14 @@ public GeoDistanceSortBuilder(StreamInput in) throws IOException {
         unit = DistanceUnit.readFromStream(in);
         order = SortOrder.readFromStream(in);
         sortMode = in.readOptionalWriteable(SortMode::readFromStream);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            if (in.readOptionalNamedWriteable(QueryBuilder.class) != null || in.readOptionalString() != null) {
+                throw new IOException(
+                    "the [sort] options [nested_path] and [nested_filter] are removed in 8.x, " + "please use [nested] instead"
+                );
+            }
+
+        }
         nestedSort = in.readOptionalWriteable(NestedSortBuilder::new);
         validation = GeoValidationMethod.readFromStream(in);
         ignoreUnmapped = in.readBoolean();
@@ -174,6 +184,10 @@ public void writeTo(StreamOutput out) throws IOException {
         unit.writeTo(out);
         order.writeTo(out);
         out.writeOptionalWriteable(sortMode);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalNamedWriteable(null);
+            out.writeOptionalString(null);
+        }
         out.writeOptionalWriteable(nestedSort);
         validation.writeTo(out);
         out.writeBoolean(ignoreUnmapped);
diff --git a/server/src/main/java/org/elasticsearch/search/sort/ScriptSortBuilder.java b/server/src/main/java/org/elasticsearch/search/sort/ScriptSortBuilder.java
index a8a06008c3971..106b483790fe3 100644
--- a/server/src/main/java/org/elasticsearch/search/sort/ScriptSortBuilder.java
+++ b/server/src/main/java/org/elasticsearch/search/sort/ScriptSortBuilder.java
@@ -16,6 +16,7 @@
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.BytesRefBuilder;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
@@ -31,6 +32,7 @@
 import org.elasticsearch.index.fielddata.fieldcomparator.BytesRefFieldComparatorSource;
 import org.elasticsearch.index.fielddata.fieldcomparator.DoubleValuesComparatorSource;
 import org.elasticsearch.index.mapper.MappedFieldType;
+import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.index.query.QueryRewriteContext;
 import org.elasticsearch.index.query.QueryShardException;
 import org.elasticsearch.index.query.SearchExecutionContext;
@@ -110,6 +112,13 @@ public ScriptSortBuilder(StreamInput in) throws IOException {
         type = ScriptSortType.readFromStream(in);
         order = SortOrder.readFromStream(in);
         sortMode = in.readOptionalWriteable(SortMode::readFromStream);
+        if (in.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            if (in.readOptionalNamedWriteable(QueryBuilder.class) != null || in.readOptionalString() != null) {
+                throw new IOException(
+                    "the [sort] options [nested_path] and [nested_filter] are removed in 8.x, " + "please use [nested] instead"
+                );
+            }
+        }
         nestedSort = in.readOptionalWriteable(NestedSortBuilder::new);
     }
 
@@ -119,6 +128,10 @@ public void writeTo(StreamOutput out) throws IOException {
         type.writeTo(out);
         order.writeTo(out);
         out.writeOptionalWriteable(sortMode);
+        if (out.getTransportVersion().before(TransportVersions.V_8_0_0)) {
+            out.writeOptionalString(null);
+            out.writeOptionalNamedWriteable(null);
+        }
         out.writeOptionalWriteable(nestedSort);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/search/vectors/KnnVectorQueryBuilder.java b/server/src/main/java/org/elasticsearch/search/vectors/KnnVectorQueryBuilder.java
index 9b252437cb004..a47c3482be3fe 100644
--- a/server/src/main/java/org/elasticsearch/search/vectors/KnnVectorQueryBuilder.java
+++ b/server/src/main/java/org/elasticsearch/search/vectors/KnnVectorQueryBuilder.java
@@ -679,6 +679,6 @@ protected boolean doEquals(KnnVectorQueryBuilder other) {
 
     @Override
     public TransportVersion getMinimalSupportedVersion() {
-        return TransportVersion.minimumCompatible();
+        return TransportVersions.V_8_0_0;
     }
 }
diff --git a/server/src/main/java/org/elasticsearch/transport/Header.java b/server/src/main/java/org/elasticsearch/transport/Header.java
index 3de52591cdd04..468bdb6e58e9f 100644
--- a/server/src/main/java/org/elasticsearch/transport/Header.java
+++ b/server/src/main/java/org/elasticsearch/transport/Header.java
@@ -10,6 +10,7 @@
 package org.elasticsearch.transport;
 
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.core.Tuple;
@@ -95,7 +96,7 @@ void finishParsingHeader(StreamInput input) throws IOException {
         this.headers = ThreadContext.readHeadersFromStream(input);
 
         if (isRequest()) {
-            if (version.equals(TransportHandshaker.V8_HANDSHAKE_VERSION)) {
+            if (version.before(TransportVersions.V_8_0_0)) {
                 // discard features
                 input.readStringArray();
             }
diff --git a/server/src/main/java/org/elasticsearch/transport/OutboundHandler.java b/server/src/main/java/org/elasticsearch/transport/OutboundHandler.java
index ffd3866d64536..5243d371ae96c 100644
--- a/server/src/main/java/org/elasticsearch/transport/OutboundHandler.java
+++ b/server/src/main/java/org/elasticsearch/transport/OutboundHandler.java
@@ -14,6 +14,7 @@
 import org.apache.logging.log4j.Logger;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.common.Strings;
@@ -297,8 +298,7 @@ public static BytesReference serialize(
         byteStreamOutput.skip(TcpHeader.HEADER_SIZE);
         threadContext.writeTo(byteStreamOutput);
         if (messageDirection == MessageDirection.REQUEST) {
-            // although we won't write a v8 handshake in production, tests for reading v8 handshakes need this condition for writing
-            if (version.equals(TransportHandshaker.V8_HANDSHAKE_VERSION)) {
+            if (version.before(TransportVersions.V_8_0_0)) {
                 // empty features array
                 byteStreamOutput.writeStringArray(Strings.EMPTY_ARRAY);
             }
diff --git a/server/src/main/java/org/elasticsearch/transport/TransportLogger.java b/server/src/main/java/org/elasticsearch/transport/TransportLogger.java
index 56338808deae2..17338289a15fa 100644
--- a/server/src/main/java/org/elasticsearch/transport/TransportLogger.java
+++ b/server/src/main/java/org/elasticsearch/transport/TransportLogger.java
@@ -11,6 +11,7 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.TransportVersion;
+import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
@@ -89,6 +90,10 @@ private static String format(TcpChannel channel, BytesReference message, String
                 ThreadContext.readHeadersFromStream(streamInput);
 
                 if (isRequest) {
+                    if (version.before(TransportVersions.V_8_0_0)) {
+                        // discard features
+                        streamInput.readStringArray();
+                    }
                     sb.append(", action: ").append(streamInput.readString());
                 }
                 sb.append(']');