diff --git a/server/src/main/java/org/elasticsearch/transport/InboundHandler.java b/server/src/main/java/org/elasticsearch/transport/InboundHandler.java
index 01069609ac742..20055ee92f187 100644
--- a/server/src/main/java/org/elasticsearch/transport/InboundHandler.java
+++ b/server/src/main/java/org/elasticsearch/transport/InboundHandler.java
@@ -32,8 +32,8 @@
 import java.nio.ByteBuffer;
 
 /**
- * Handles inbound messages by first deserializing a {@link TransportMessage} from an {@link InboundMessage} and then passing
- * it to the appropriate handler.
+ * Handles inbound messages by first deserializing a {@link TransportRequest} or {@link TransportResponse} from an {@link InboundMessage}
+ * and then passing it to the appropriate handler.
  */
 public class InboundHandler {
 
diff --git a/server/src/test/java/org/elasticsearch/action/search/SearchPhaseControllerTests.java b/server/src/test/java/org/elasticsearch/action/search/SearchPhaseControllerTests.java
index c95a155a790fd..b98c6d662f692 100644
--- a/server/src/test/java/org/elasticsearch/action/search/SearchPhaseControllerTests.java
+++ b/server/src/test/java/org/elasticsearch/action/search/SearchPhaseControllerTests.java
@@ -36,6 +36,7 @@
 import org.elasticsearch.common.util.concurrent.EsExecutors;
 import org.elasticsearch.common.util.concurrent.EsExecutors.TaskTrackingConfig;
 import org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor;
+import org.elasticsearch.core.RefCounted;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.lucene.grouping.TopFieldGroups;
 import org.elasticsearch.search.DocValueFormat;
@@ -71,7 +72,6 @@
 import org.elasticsearch.test.InternalAggregationTestCase;
 import org.elasticsearch.threadpool.TestThreadPool;
 import org.elasticsearch.threadpool.ThreadPool;
-import org.elasticsearch.transport.TransportMessage;
 import org.junit.After;
 import org.junit.Before;
 
@@ -178,7 +178,7 @@ public void testSortDocs() {
             ScoreDoc[] sortedDocs = SearchPhaseController.sortDocs(true, topDocsList, from, size, reducedCompletionSuggestions).scoreDocs();
             assertThat(sortedDocs.length, equalTo(accumulatedLength));
         } finally {
-            results.asList().forEach(TransportMessage::decRef);
+            results.asList().forEach(RefCounted::decRef);
         }
     }
 
@@ -212,7 +212,7 @@ public void testSortDocsIsIdempotent() throws Exception {
             }
             sortedDocs = SearchPhaseController.sortDocs(ignoreFrom, topDocsList, from, size, Collections.emptyList()).scoreDocs();
         } finally {
-            results.asList().forEach(TransportMessage::decRef);
+            results.asList().forEach(RefCounted::decRef);
         }
         results = generateSeededQueryResults(randomSeed, nShards, Collections.emptyList(), queryResultSize, useConstantScore);
         try {
@@ -232,7 +232,7 @@ public void testSortDocsIsIdempotent() throws Exception {
                 assertEquals(sortedDocs[i].score, sortedDocs2[i].score, 0.0f);
             }
         } finally {
-            results.asList().forEach(TransportMessage::decRef);
+            results.asList().forEach(RefCounted::decRef);
         }
     }
 
@@ -345,10 +345,10 @@ public void testMerge() {
                         assertThat(mergedResponse.profile(), is(anEmptyMap()));
                     }
                 } finally {
-                    fetchResults.asList().forEach(TransportMessage::decRef);
+                    fetchResults.asList().forEach(RefCounted::decRef);
                 }
             } finally {
-                queryResults.asList().forEach(TransportMessage::decRef);
+                queryResults.asList().forEach(RefCounted::decRef);
             }
         }
     }
@@ -424,11 +424,11 @@ protected boolean lessThan(RankDoc a, RankDoc b) {
                     assertThat(mergedResponse.hits().getHits().length, equalTo(reducedQueryPhase.sortedTopDocs().scoreDocs().length));
                     assertThat(mergedResponse.profile(), is(anEmptyMap()));
                 } finally {
-                    fetchResults.asList().forEach(TransportMessage::decRef);
+                    fetchResults.asList().forEach(RefCounted::decRef);
                 }
             } finally {
 
-                queryResults.asList().forEach(TransportMessage::decRef);
+                queryResults.asList().forEach(RefCounted::decRef);
             }
         }
     }
diff --git a/server/src/test/java/org/elasticsearch/search/profile/SearchProfileResultsBuilderTests.java b/server/src/test/java/org/elasticsearch/search/profile/SearchProfileResultsBuilderTests.java
index cd9249c98de3e..629e51b352b89 100644
--- a/server/src/test/java/org/elasticsearch/search/profile/SearchProfileResultsBuilderTests.java
+++ b/server/src/test/java/org/elasticsearch/search/profile/SearchProfileResultsBuilderTests.java
@@ -10,12 +10,12 @@
 package org.elasticsearch.search.profile;
 
 import org.elasticsearch.common.util.Maps;
+import org.elasticsearch.core.RefCounted;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.search.SearchHits;
 import org.elasticsearch.search.SearchShardTarget;
 import org.elasticsearch.search.fetch.FetchSearchResult;
 import org.elasticsearch.test.ESTestCase;
-import org.elasticsearch.transport.TransportMessage;
 
 import java.util.List;
 import java.util.Map;
@@ -77,7 +77,7 @@ public void testQueryAndFetch() {
                 equalTo((long) searchPhase.size())
             );
         } finally {
-            fetchPhase.forEach(TransportMessage::decRef);
+            fetchPhase.forEach(RefCounted::decRef);
         }
     }
 
diff --git a/server/src/test/java/org/elasticsearch/transport/InboundDecoderTests.java b/server/src/test/java/org/elasticsearch/transport/InboundDecoderTests.java
index 34a7fb9cf167d..d91d2cfb4bae3 100644
--- a/server/src/test/java/org/elasticsearch/transport/InboundDecoderTests.java
+++ b/server/src/test/java/org/elasticsearch/transport/InboundDecoderTests.java
@@ -15,6 +15,7 @@
 import org.elasticsearch.common.bytes.ReleasableBytesReference;
 import org.elasticsearch.common.io.stream.BytesStreamOutput;
 import org.elasticsearch.common.io.stream.RecyclerBytesStreamOutput;
+import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.MockPageCacheRecycler;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
@@ -376,7 +377,7 @@ public void testCompressedDecode() throws IOException {
         Compression.Scheme scheme = randomFrom(Compression.Scheme.DEFLATE, Compression.Scheme.LZ4);
 
         try (RecyclerBytesStreamOutput os = new RecyclerBytesStreamOutput(recycler)) {
-            final TransportMessage transportMessage = isRequest
+            final Writeable transportMessage = isRequest
                 ? new TestRequest(randomAlphaOfLength(100))
                 : new TestResponse(randomAlphaOfLength(100));
             final BytesReference totalBytes = OutboundHandler.serialize(
diff --git a/server/src/test/java/org/elasticsearch/transport/TransportActionProxyTests.java b/server/src/test/java/org/elasticsearch/transport/TransportActionProxyTests.java
index 46585ac382583..7b0a9f6ccbed4 100644
--- a/server/src/test/java/org/elasticsearch/transport/TransportActionProxyTests.java
+++ b/server/src/test/java/org/elasticsearch/transport/TransportActionProxyTests.java
@@ -159,7 +159,7 @@ public void testSendMessage() throws InterruptedException {
         TransportActionProxy.registerProxyAction(serviceC, "internal:test", cancellable, SimpleTestResponse::new);
         // Node A -> Node B -> Node C: different versions - serialize the response
         {
-            final List<TransportMessage> responses = Collections.synchronizedList(new ArrayList<>());
+            final List<TransportResponse> responses = Collections.synchronizedList(new ArrayList<>());
             final CountDownLatch latch = new CountDownLatch(1);
             serviceB.addRequestHandlingBehavior(
                 TransportActionProxy.getProxyAction("internal:test"),
@@ -212,7 +212,7 @@ public void handleException(TransportException exp) {
         {
             AbstractSimpleTransportTestCase.connectToNode(serviceD, nodeB);
             final CountDownLatch latch = new CountDownLatch(1);
-            final List<TransportMessage> responses = Collections.synchronizedList(new ArrayList<>());
+            final List<TransportResponse> responses = Collections.synchronizedList(new ArrayList<>());
             serviceB.addRequestHandlingBehavior(
                 TransportActionProxy.getProxyAction("internal:test"),
                 (handler, request, channel, task) -> handler.messageReceived(
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/AuthenticationFailureHandler.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/AuthenticationFailureHandler.java
index 6a2cf608d21df..682072598c04f 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/AuthenticationFailureHandler.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/AuthenticationFailureHandler.java
@@ -9,7 +9,7 @@
 import org.elasticsearch.ElasticsearchSecurityException;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.http.HttpPreRequest;
-import org.elasticsearch.transport.TransportMessage;
+import org.elasticsearch.transport.TransportRequest;
 
 /**
  * A AuthenticationFailureHandler is responsible for the handling of a request that has failed authentication. This must
@@ -51,7 +51,7 @@ public interface AuthenticationFailureHandler {
      * @return ElasticsearchSecurityException with the appropriate headers and message
      */
     ElasticsearchSecurityException failedAuthentication(
-        TransportMessage message,
+        TransportRequest message,
         AuthenticationToken token,
         String action,
         ThreadContext context
@@ -78,7 +78,7 @@ ElasticsearchSecurityException failedAuthentication(
      * @param context The context of the request that failed authentication that could not be authenticated
      * @return ElasticsearchSecurityException with the appropriate headers and message
      */
-    ElasticsearchSecurityException exceptionProcessingRequest(TransportMessage message, String action, Exception e, ThreadContext context);
+    ElasticsearchSecurityException exceptionProcessingRequest(TransportRequest message, String action, Exception e, ThreadContext context);
 
     /**
      * This method is called when a REST request is received and no authentication token could be extracted AND anonymous
@@ -99,7 +99,7 @@ ElasticsearchSecurityException failedAuthentication(
      * @param context The context of the request that failed authentication that could not be authenticated
      * @return ElasticsearchSecurityException with the appropriate headers and message
      */
-    ElasticsearchSecurityException missingToken(TransportMessage message, String action, ThreadContext context);
+    ElasticsearchSecurityException missingToken(TransportRequest message, String action, ThreadContext context);
 
     /**
      * This method is called when anonymous access is enabled, a request does not pass authorization with the anonymous
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/DefaultAuthenticationFailureHandler.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/DefaultAuthenticationFailureHandler.java
index c9b30a826248a..21a316f2cd1ec 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/DefaultAuthenticationFailureHandler.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/DefaultAuthenticationFailureHandler.java
@@ -11,7 +11,7 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.http.HttpPreRequest;
 import org.elasticsearch.rest.RestStatus;
-import org.elasticsearch.transport.TransportMessage;
+import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.xpack.core.XPackField;
 
 import java.util.ArrayList;
@@ -98,7 +98,7 @@ public ElasticsearchSecurityException failedAuthentication(HttpPreRequest reques
 
     @Override
     public ElasticsearchSecurityException failedAuthentication(
-        TransportMessage message,
+        TransportRequest message,
         AuthenticationToken token,
         String action,
         ThreadContext context
@@ -118,7 +118,7 @@ public ElasticsearchSecurityException exceptionProcessingRequest(HttpPreRequest
 
     @Override
     public ElasticsearchSecurityException exceptionProcessingRequest(
-        TransportMessage message,
+        TransportRequest message,
         String action,
         Exception e,
         ThreadContext context
@@ -137,7 +137,7 @@ public ElasticsearchSecurityException missingToken(HttpPreRequest request, Threa
     }
 
     @Override
-    public ElasticsearchSecurityException missingToken(TransportMessage message, String action, ThreadContext context) {
+    public ElasticsearchSecurityException missingToken(TransportRequest message, String action, ThreadContext context) {
         return createAuthenticationError("missing authentication credentials for action [{}]", null, action);
     }
 
diff --git a/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/audit/AuditUtil.java b/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/audit/AuditUtil.java
index 58516b1d8324d..c584945bc3bd2 100644
--- a/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/audit/AuditUtil.java
+++ b/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/audit/AuditUtil.java
@@ -13,7 +13,7 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.rest.RestRequest;
-import org.elasticsearch.transport.TransportMessage;
+import org.elasticsearch.transport.TransportRequest;
 
 import java.io.IOException;
 import java.util.Arrays;
@@ -37,9 +37,9 @@ public static String restRequestContent(RestRequest request) {
         return "";
     }
 
-    public static Set<String> indices(TransportMessage message) {
-        if (message instanceof IndicesRequest) {
-            return arrayToSetOrNull(((IndicesRequest) message).indices());
+    public static Set<String> indices(TransportRequest message) {
+        if (message instanceof IndicesRequest indicesRequest) {
+            return arrayToSetOrNull(indicesRequest.indices());
         }
         return null;
     }
diff --git a/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/realm/CustomAuthenticationFailureHandler.java b/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/realm/CustomAuthenticationFailureHandler.java
index a6e545070d92f..6f28660dc8423 100644
--- a/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/realm/CustomAuthenticationFailureHandler.java
+++ b/x-pack/qa/security-example-spi-extension/src/main/java/org/elasticsearch/example/realm/CustomAuthenticationFailureHandler.java
@@ -9,7 +9,7 @@
 import org.elasticsearch.ElasticsearchSecurityException;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.http.HttpPreRequest;
-import org.elasticsearch.transport.TransportMessage;
+import org.elasticsearch.transport.TransportRequest;
 import org.elasticsearch.xpack.core.security.authc.AuthenticationToken;
 import org.elasticsearch.xpack.core.security.authc.DefaultAuthenticationFailureHandler;
 
@@ -31,7 +31,7 @@ public ElasticsearchSecurityException failedAuthentication(HttpPreRequest reques
 
     @Override
     public ElasticsearchSecurityException failedAuthentication(
-        TransportMessage message,
+        TransportRequest message,
         AuthenticationToken token,
         String action,
         ThreadContext context
@@ -51,7 +51,7 @@ public ElasticsearchSecurityException missingToken(HttpPreRequest request, Threa
     }
 
     @Override
-    public ElasticsearchSecurityException missingToken(TransportMessage message, String action, ThreadContext context) {
+    public ElasticsearchSecurityException missingToken(TransportRequest message, String action, ThreadContext context) {
         ElasticsearchSecurityException e = super.missingToken(message, action, context);
         // set a custom header
         e.addHeader("WWW-Authenticate", "custom-challenge");