diff --git a/lib/cast.js b/lib/cast.js
index d5ea75227b9..f91cdb007dc 100644
--- a/lib/cast.js
+++ b/lib/cast.js
@@ -79,7 +79,7 @@ module.exports = function cast(schema, obj, options, context) {
           val[k] = cast(discriminatorSchema ? discriminatorSchema : schema, val[k], options, context);
         }
 
-        if (Object.keys(val[k]).length === 0 && beforeCastKeysLength !== 0) {
+        if (utils.hasOwnKeys(val[k]) === false && beforeCastKeysLength !== 0) {
           val.splice(k, 1);
         }
       }
@@ -126,10 +126,7 @@ module.exports = function cast(schema, obj, options, context) {
           const pathFirstHalf = split.slice(0, j).join('.');
           const pathLastHalf = split.slice(j).join('.');
           const _schematype = schema.path(pathFirstHalf);
-          const discriminatorKey = _schematype &&
-            _schematype.schema &&
-            _schematype.schema.options &&
-            _schematype.schema.options.discriminatorKey;
+          const discriminatorKey = _schematype?.schema?.options?.discriminatorKey;
 
           // gh-6027: if we haven't found the schematype but this path is
           // underneath an embedded discriminator and the embedded discriminator
@@ -430,11 +427,7 @@ function getStrictQuery(queryOptions, schemaUserProvidedOptions, schemaOptions,
   if ('strictQuery' in schemaUserProvidedOptions) {
     return schemaUserProvidedOptions.strictQuery;
   }
-  const mongooseOptions = context &&
-    context.mongooseCollection &&
-    context.mongooseCollection.conn &&
-    context.mongooseCollection.conn.base &&
-    context.mongooseCollection.conn.base.options;
+  const mongooseOptions = context?.mongooseCollection?.conn?.base?.options;
   if (mongooseOptions) {
     if ('strictQuery' in mongooseOptions) {
       return mongooseOptions.strictQuery;
diff --git a/lib/connection.js b/lib/connection.js
index 8d9d27e8ff0..d31138e63cb 100644
--- a/lib/connection.js
+++ b/lib/connection.js
@@ -630,7 +630,7 @@ Connection.prototype.createCollections = async function createCollections(option
     }
   }
 
-  if (!continueOnError && Object.keys(errorsMap).length) {
+  if (!continueOnError && utils.hasOwnKeys(errorsMap)) {
     const message = Object.entries(errorsMap).map(([modelName, err]) => `${modelName}: ${err.message}`).join(', ');
     const createCollectionsError = new CreateCollectionsError(message, errorsMap);
     throw createCollectionsError;
@@ -1250,8 +1250,11 @@ Connection.prototype._close = async function _close(force, destroy) {
   const conn = this;
   switch (this.readyState) {
     case STATES.disconnected:
-      if (destroy && this.base.connections.indexOf(conn) !== -1) {
-        this.base.connections.splice(this.base.connections.indexOf(conn), 1);
+      if (destroy) {
+        const index = this.base.connections.indexOf(conn);
+        if (index !== -1) {
+          this.base.connections.splice(index, 1);
+        }
       }
       if (!closeCalled) {
         await this.doClose(force);
@@ -1262,8 +1265,11 @@ Connection.prototype._close = async function _close(force, destroy) {
     case STATES.connected:
       this.readyState = STATES.disconnecting;
       await this.doClose(force);
-      if (destroy && _this.base.connections.indexOf(conn) !== -1) {
-        this.base.connections.splice(this.base.connections.indexOf(conn), 1);
+      if (destroy) {
+        const index = _this.base.connections.indexOf(conn);
+        if (index !== -1) {
+          this.base.connections.splice(index, 1);
+        }
       }
       this.onClose(force);
 
@@ -1772,7 +1778,7 @@ Connection.prototype.syncIndexes = async function syncIndexes(options = {}) {
     }
   }
 
-  if (!continueOnError && Object.keys(errorsMap).length) {
+  if (!continueOnError && utils.hasOwnKeys(errorsMap)) {
     const message = Object.entries(errorsMap).map(([modelName, err]) => `${modelName}: ${err.message}`).join(', ');
     const syncIndexesError = new SyncIndexesError(message, errorsMap);
     throw syncIndexesError;
diff --git a/lib/cursor/changeStream.js b/lib/cursor/changeStream.js
index b41e2379e83..3221a29fb9c 100644
--- a/lib/cursor/changeStream.js
+++ b/lib/cursor/changeStream.js
@@ -83,7 +83,7 @@ class ChangeStream extends EventEmitter {
 
           driverChangeStreamEvents.forEach(ev => {
             this.driverChangeStream.on(ev, data => {
-              if (data != null && data.fullDocument != null && this.options && this.options.hydrate) {
+              if (data?.fullDocument != null && this.options?.hydrate) {
                 data.fullDocument = this.options.model.hydrate(data.fullDocument);
               }
               this.emit(ev, data);
@@ -102,7 +102,7 @@ class ChangeStream extends EventEmitter {
 
     driverChangeStreamEvents.forEach(ev => {
       this.driverChangeStream.on(ev, data => {
-        if (data != null && data.fullDocument != null && this.options && this.options.hydrate) {
+        if (data?.fullDocument != null && this.options?.hydrate) {
           data.fullDocument = this.options.model.hydrate(data.fullDocument);
         }
         this.emit(ev, data);
diff --git a/lib/document.js b/lib/document.js
index 45da5eb3f13..2a5f97b1219 100644
--- a/lib/document.js
+++ b/lib/document.js
@@ -149,7 +149,7 @@ function Document(obj, fields, options) {
 
   // determine if this doc is a result of a query with
   // excluded fields
-  if (utils.isPOJO(fields) && Object.keys(fields).length > 0) {
+  if (utils.isPOJO(fields) && utils.hasOwnKeys(fields)) {
     exclude = isExclusive(fields);
     this.$__.selected = fields;
     this.$__.exclude = exclude;
@@ -1015,17 +1015,21 @@ Document.prototype.$timestamps = function $timestamps(value) {
  */
 
 Document.prototype.overwrite = function overwrite(obj) {
-  const keys = Array.from(new Set(Object.keys(this._doc).concat(Object.keys(obj))));
+  const keys = new Set(Object.keys(this._doc));
+  for (const key of Object.keys(obj)) {
+    keys.add(key);
+  }
 
+  const schemaOptions = this.$__schema.options;
   for (const key of keys) {
     if (key === '_id') {
       continue;
     }
     // Explicitly skip version key
-    if (this.$__schema.options.versionKey && key === this.$__schema.options.versionKey) {
+    if (schemaOptions.versionKey && key === schemaOptions.versionKey) {
       continue;
     }
-    if (this.$__schema.options.discriminatorKey && key === this.$__schema.options.discriminatorKey) {
+    if (schemaOptions.discriminatorKey && key === schemaOptions.discriminatorKey) {
       continue;
     }
     this.$set(key, obj[key]);
@@ -1697,7 +1701,7 @@ Document.prototype.$__set = function(pathToMark, path, options, constructing, pa
   if (shouldModify) {
     if (this.$__.primitiveAtomics && this.$__.primitiveAtomics[path]) {
       delete this.$__.primitiveAtomics[path];
-      if (Object.keys(this.$__.primitiveAtomics).length === 0) {
+      if (utils.hasOwnKeys(this.$__.primitiveAtomics) === false) {
         delete this.$__.primitiveAtomics;
       }
     }
@@ -3001,7 +3005,7 @@ Document.prototype.$__validate = async function $__validate(pathsToValidate, opt
           delete validationError.errors[errPath];
         }
       }
-      if (Object.keys(validationError.errors).length === 0) {
+      if (utils.hasOwnKeys(validationError.errors) === false) {
         validationError = void 0;
       }
     }
@@ -3402,7 +3406,7 @@ Document.prototype.$markValid = function(path) {
   }
 
   delete this.$__.validationError.errors[path];
-  if (Object.keys(this.$__.validationError.errors).length === 0) {
+  if (utils.hasOwnKeys(this.$__.validationError.errors) === false) {
     this.$__.validationError = null;
   }
 };
@@ -3422,7 +3426,7 @@ function _markValidSubpaths(doc, path) {
       delete doc.$__.validationError.errors[key];
     }
   }
-  if (Object.keys(doc.$__.validationError.errors).length === 0) {
+  if (utils.hasOwnKeys(doc.$__.validationError.errors) === false) {
     doc.$__.validationError = null;
   }
 }
@@ -3497,7 +3501,7 @@ function _checkImmutableSubpaths(subdoc, schematype, priorVal) {
  */
 
 Document.prototype.$isValid = function(path) {
-  if (this.$__.validationError == null || Object.keys(this.$__.validationError.errors).length === 0) {
+  if (this.$__.validationError == null || utils.hasOwnKeys(this.$__.validationError.errors) === false) {
     return true;
   }
   if (path == null) {
@@ -4375,7 +4379,7 @@ function omitDeselectedFields(self, json) {
     selected = {};
     queryhelpers.applyPaths(selected, schema);
   }
-  if (selected == null || Object.keys(selected).length === 0) {
+  if (selected == null || utils.hasOwnKeys(selected) === false) {
     return json;
   }
 
@@ -5057,7 +5061,7 @@ Document.prototype.$__delta = function $__delta() {
     this.$__version(where, delta);
   }
 
-  if (Object.keys(delta).length === 0) {
+  if (utils.hasOwnKeys(delta) === false) {
     return [where, null];
   }
 
@@ -5109,7 +5113,7 @@ function checkDivergentArray(doc, path, array) {
 
   if (check) {
     const atomics = array[arrayAtomicsSymbol];
-    if (Object.keys(atomics).length === 0 || atomics.$set || atomics.$pop) {
+    if (utils.hasOwnKeys(atomics) === false || atomics.$set || atomics.$pop) {
       return path;
     }
   }
diff --git a/lib/drivers/node-mongodb-native/collection.js b/lib/drivers/node-mongodb-native/collection.js
index 1e4678ff93f..cf25c74ddc6 100644
--- a/lib/drivers/node-mongodb-native/collection.js
+++ b/lib/drivers/node-mongodb-native/collection.js
@@ -97,15 +97,8 @@ function iter(i) {
     const collection = this._getCollection();
     const args = Array.from(arguments);
     const _this = this;
-    const globalDebug = _this &&
-      _this.conn &&
-      _this.conn.base &&
-      _this.conn.base.options &&
-      _this.conn.base.options.debug;
-    const connectionDebug = _this &&
-      _this.conn &&
-      _this.conn.options &&
-      _this.conn.options.debug;
+    const globalDebug = _this?.conn?.base?.options?.debug;
+    const connectionDebug = _this?.conn?.options?.debug;
     const debug = connectionDebug == null ? globalDebug : connectionDebug;
     const lastArg = arguments[arguments.length - 1];
     const opId = new ObjectId();
@@ -428,12 +421,7 @@ function format(obj, sub, color, shell) {
           formatDate(x, key, shell);
         } else if (_constructorName === 'ClientSession') {
           x[key] = inspectable('ClientSession("' +
-            (
-              x[key] &&
-              x[key].id &&
-              x[key].id.id &&
-              x[key].id.id.buffer || ''
-            ).toString('hex') + '")');
+            (x[key]?.id?.id?.buffer || '').toString('hex') + '")');
         } else if (Array.isArray(x[key])) {
           x[key] = x[key].map(map);
         } else if (error != null) {
diff --git a/lib/drivers/node-mongodb-native/connection.js b/lib/drivers/node-mongodb-native/connection.js
index 3f4be863c2e..6ff3e03d91b 100644
--- a/lib/drivers/node-mongodb-native/connection.js
+++ b/lib/drivers/node-mongodb-native/connection.js
@@ -316,15 +316,15 @@ NativeConnection.prototype.createClient = async function createClient(uri, optio
 
   const { schemaMap, encryptedFieldsMap } = this._buildEncryptionSchemas();
 
-  if ((Object.keys(schemaMap).length > 0 || Object.keys(encryptedFieldsMap).length) && !options.autoEncryption) {
+  if ((utils.hasOwnKeys(schemaMap) || utils.hasOwnKeys(encryptedFieldsMap)) && !options.autoEncryption) {
     throw new Error('Must provide `autoEncryption` when connecting with encrypted schemas.');
   }
 
-  if (Object.keys(schemaMap).length > 0) {
+  if (utils.hasOwnKeys(schemaMap)) {
     options.autoEncryption.schemaMap = schemaMap;
   }
 
-  if (Object.keys(encryptedFieldsMap).length > 0) {
+  if (utils.hasOwnKeys(encryptedFieldsMap)) {
     options.autoEncryption.encryptedFieldsMap = encryptedFieldsMap;
   }
 
@@ -435,18 +435,8 @@ function _setClient(conn, client, options, dbName) {
   const db = dbName != null ? client.db(dbName) : client.db();
   conn.db = db;
   conn.client = client;
-  conn.host = client &&
-    client.s &&
-    client.s.options &&
-    client.s.options.hosts &&
-    client.s.options.hosts[0] &&
-    client.s.options.hosts[0].host || void 0;
-  conn.port = client &&
-    client.s &&
-    client.s.options &&
-    client.s.options.hosts &&
-    client.s.options.hosts[0] &&
-    client.s.options.hosts[0].port || void 0;
+  conn.host = client?.s?.options?.hosts?.[0]?.host;
+  conn.port = client?.s?.options?.hosts?.[0]?.port;
   conn.name = dbName != null ? dbName : db.databaseName;
   conn._closeCalled = client._closeCalled;
 
@@ -463,10 +453,7 @@ function _setClient(conn, client, options, dbName) {
     }
   };
 
-  const type = client &&
-  client.topology &&
-  client.topology.description &&
-  client.topology.description.type || '';
+  const type = client?.topology?.description?.type || '';
 
   if (type === 'Single') {
     client.on('serverDescriptionChanged', ev => {
diff --git a/lib/helpers/document/applyTimestamps.js b/lib/helpers/document/applyTimestamps.js
index 425e144c867..c26146bfa1c 100644
--- a/lib/helpers/document/applyTimestamps.js
+++ b/lib/helpers/document/applyTimestamps.js
@@ -2,6 +2,7 @@
 
 const handleTimestampOption = require('../schema/handleTimestampOption');
 const mpath = require('mpath');
+const utils = require('../../utils');
 
 module.exports = applyTimestamps;
 
@@ -71,7 +72,7 @@ function applyTimestampsToDoc(schema, obj, options) {
     return;
   }
 
-  if (schema.discriminators && Object.keys(schema.discriminators).length > 0) {
+  if (schema.discriminators && utils.hasOwnKeys(schema.discriminators)) {
     for (const discriminatorKey of Object.keys(schema.discriminators)) {
       const discriminator = schema.discriminators[discriminatorKey];
       const key = discriminator.discriminatorMapping.key;
diff --git a/lib/helpers/document/applyVirtuals.js b/lib/helpers/document/applyVirtuals.js
index 5fbe7ca82ba..09a61f8a2c5 100644
--- a/lib/helpers/document/applyVirtuals.js
+++ b/lib/helpers/document/applyVirtuals.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const mpath = require('mpath');
+const utils = require('../../utils');
 
 module.exports = applyVirtuals;
 
@@ -101,7 +102,7 @@ function applyVirtualsToDoc(schema, obj, virtuals) {
     return;
   }
 
-  if (schema.discriminators && Object.keys(schema.discriminators).length > 0) {
+  if (schema.discriminators && utils.hasOwnKeys(schema.discriminators)) {
     for (const discriminatorKey of Object.keys(schema.discriminators)) {
       const discriminator = schema.discriminators[discriminatorKey];
       const key = discriminator.discriminatorMapping.key;
diff --git a/lib/helpers/document/compile.js b/lib/helpers/document/compile.js
index 51721e7a490..4b4350f4c2e 100644
--- a/lib/helpers/document/compile.js
+++ b/lib/helpers/document/compile.js
@@ -46,7 +46,7 @@ function compile(tree, proto, prefix, options) {
     const limb = tree[key];
 
     const hasSubprops = isPOJO(limb) &&
-      Object.keys(limb).length > 0 &&
+      utils.hasOwnKeys(limb) &&
       (!limb[typeKey] || (typeKey === 'type' && isPOJO(limb.type) && limb.type.type));
     const subprops = hasSubprops ? limb : null;
 
@@ -132,7 +132,7 @@ function defineKey({ prop, subprops, prototype, prefix, options }) {
             writable: false,
             value: function() {
               return _this.get(path, null, {
-                virtuals: this && this.schema && this.schema.options && this.schema.options.toObject && this.schema.options.toObject.virtuals || null
+                virtuals: this?.schema?.options?.toObject?.virtuals || null
               });
             }
           });
@@ -143,7 +143,7 @@ function defineKey({ prop, subprops, prototype, prefix, options }) {
             writable: false,
             value: function() {
               return _this.get(path, null, {
-                virtuals: this && this.schema && this.schema.options && this.schema.options.toJSON && this.schema.options.toJSON.virtuals || null
+                virtuals: this?.schema?.options?.toJSON?.virtuals || null
               });
             }
           });
diff --git a/lib/helpers/populate/getModelsMapForPopulate.js b/lib/helpers/populate/getModelsMapForPopulate.js
index 7d1b3f47fde..56a4d690d7b 100644
--- a/lib/helpers/populate/getModelsMapForPopulate.js
+++ b/lib/helpers/populate/getModelsMapForPopulate.js
@@ -26,6 +26,7 @@ module.exports = function getModelsMapForPopulate(model, docs, options) {
   let schema;
   let refPath;
   let modelNames;
+  let modelNamesSet;
   const available = {};
 
   const modelSchema = model.schema;
@@ -123,8 +124,10 @@ module.exports = function getModelsMapForPopulate(model, docs, options) {
           continue;
         }
         modelNames = modelNames || [];
+        modelNamesSet = modelNamesSet || new Set();
         for (const modelName of _modelNames) {
-          if (modelNames.indexOf(modelName) === -1) {
+          if (modelNamesSet.has(modelName) === false) {
+            modelNamesSet.add(modelName);
             modelNames.push(modelName);
           }
         }
@@ -225,8 +228,8 @@ module.exports = function getModelsMapForPopulate(model, docs, options) {
       schema = schema.$__schemaType;
     }
 
-    const ref = schema && schema.options && schema.options.ref;
-    refPath = schema && schema.options && schema.options.refPath;
+    const ref = schema?.options?.ref;
+    refPath = schema?.options?.refPath;
     if (schema != null &&
         schema[schemaMixedSymbol] &&
         !ref &&
@@ -721,7 +724,7 @@ function _findRefPathForDiscriminators(doc, modelSchema, data, options, normaliz
     if (schematype != null &&
         schematype.$isMongooseDocumentArray &&
         schematype.Constructor.discriminators != null &&
-        Object.keys(schematype.Constructor.discriminators).length !== 0) {
+        utils.hasOwnKeys(schematype.Constructor.discriminators)) {
       const subdocs = utils.getValue(cur, doc);
       const remnant = options.path.substring(cur.length + 1);
       const discriminatorKey = schematype.Constructor.schema.options.discriminatorKey;
diff --git a/lib/helpers/query/castUpdate.js b/lib/helpers/query/castUpdate.js
index bc8bdf627bb..75b22b6f2ff 100644
--- a/lib/helpers/query/castUpdate.js
+++ b/lib/helpers/query/castUpdate.js
@@ -153,9 +153,9 @@ module.exports = function castUpdate(schema, obj, options, context, filter) {
     }
   }
 
-  if (Object.keys(ret).length === 0 &&
+  if (utils.hasOwnKeys(ret) === false &&
       options.upsert &&
-      Object.keys(filter).length > 0) {
+      utils.hasOwnKeys(filter)) {
     // Trick the driver into allowing empty upserts to work around
     // https://github.com/mongodb/node-mongodb-native/pull/2490
     // Shallow clone to avoid passing defaults in re: gh-13962
@@ -376,7 +376,7 @@ function walkUpdatePath(schema, obj, op, options, context, filter, prefix) {
         // we should be able to set a schema-less field
         // to an empty object literal
         hasKeys |= walkUpdatePath(schema, val, op, options, context, filter, prefix + key) ||
-          (utils.isObject(val) && Object.keys(val).length === 0);
+          (utils.isObject(val) && utils.hasOwnKeys(val) === false);
       }
     } else {
       const isModifier = (key === '$each' || key === '$or' || key === '$and' || key === '$in');
diff --git a/lib/helpers/schema/applyReadConcern.js b/lib/helpers/schema/applyReadConcern.js
index 050fa9c6df0..1367368abdd 100644
--- a/lib/helpers/schema/applyReadConcern.js
+++ b/lib/helpers/schema/applyReadConcern.js
@@ -9,7 +9,7 @@ module.exports = function applyReadConcern(schema, options) {
   // because you shouldn't set read concern on individual operations
   // within a transaction.
   // See: https://www.mongodb.com/docs/manual/reference/read-concern/
-  if (options && options.session && options.session.transaction) {
+  if (options?.session?.transaction) {
     return;
   }
 
diff --git a/lib/helpers/schema/applyWriteConcern.js b/lib/helpers/schema/applyWriteConcern.js
index 28338cf58c3..2b7413713a3 100644
--- a/lib/helpers/schema/applyWriteConcern.js
+++ b/lib/helpers/schema/applyWriteConcern.js
@@ -1,5 +1,7 @@
 'use strict';
 
+const utils = require('../../utils');
+
 module.exports = function applyWriteConcern(schema, options) {
   if (options.writeConcern != null) {
     return;
@@ -7,11 +9,11 @@ module.exports = function applyWriteConcern(schema, options) {
   // Don't apply default write concern to operations in transactions,
   // because setting write concern on an operation in a transaction is an error
   // See: https://www.mongodb.com/docs/manual/reference/write-concern/
-  if (options && options.session && options.session.transaction) {
+  if (options?.session?.transaction) {
     return;
   }
   const writeConcern = schema.options.writeConcern ?? {};
-  if (Object.keys(writeConcern).length != 0) {
+  if (utils.hasOwnKeys(writeConcern)) {
     options.writeConcern = {};
     if (!('w' in options) && writeConcern.w != null) {
       options.writeConcern.w = writeConcern.w;
diff --git a/lib/helpers/schema/getIndexes.js b/lib/helpers/schema/getIndexes.js
index 362b0785260..80e3a96db00 100644
--- a/lib/helpers/schema/getIndexes.js
+++ b/lib/helpers/schema/getIndexes.js
@@ -69,7 +69,7 @@ module.exports = function getIndexes(schema) {
 
       const index = path._index || (path.embeddedSchemaType && path.embeddedSchemaType._index);
 
-      if (index !== false && index !== null && index !== undefined) {
+      if (index !== false && index != null) {
         const field = {};
         const isObject = helperIsObject(index);
         const options = isObject ? { ...index } : {};
diff --git a/lib/helpers/update/applyTimestampsToUpdate.js b/lib/helpers/update/applyTimestampsToUpdate.js
index e8d3217fbb9..95f95c06641 100644
--- a/lib/helpers/update/applyTimestampsToUpdate.js
+++ b/lib/helpers/update/applyTimestampsToUpdate.js
@@ -5,6 +5,7 @@
  */
 
 const get = require('../get');
+const utils = require('../../utils');
 
 module.exports = applyTimestampsToUpdate;
 
@@ -110,7 +111,7 @@ function applyTimestampsToUpdate(now, createdAt, updatedAt, currentUpdate, optio
     }
   }
 
-  if (Object.keys(updates.$set).length === 0) {
+  if (utils.hasOwnKeys(updates.$set) === false) {
     delete updates.$set;
   }
   return updates;
diff --git a/lib/helpers/update/castArrayFilters.js b/lib/helpers/update/castArrayFilters.js
index ed59af49b7e..405c4c06704 100644
--- a/lib/helpers/update/castArrayFilters.js
+++ b/lib/helpers/update/castArrayFilters.js
@@ -4,6 +4,7 @@ const castFilterPath = require('../query/castFilterPath');
 const cleanPositionalOperators = require('../schema/cleanPositionalOperators');
 const getPath = require('../schema/getPath');
 const updatedPathsByArrayFilter = require('./updatedPathsByArrayFilter');
+const utils = require('../../utils');
 
 module.exports = function castArrayFilters(query) {
   const arrayFilters = query.options.arrayFilters;
@@ -74,7 +75,7 @@ function _castArrayFilters(arrayFilters, schema, strictQuery, updatedPathsByFilt
       if (updatedPathsByFilter[key] === null) {
         continue;
       }
-      if (Object.keys(updatedPathsByFilter).length === 0) {
+      if (utils.hasOwnKeys(updatedPathsByFilter) === false) {
         continue;
       }
       const dot = key.indexOf('.');
diff --git a/lib/model.js b/lib/model.js
index 74d990b68c4..2f7935cd173 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -434,7 +434,7 @@ Model.prototype.$__save = async function $__save(options) {
                 continue;
               }
               minimize(updateOp[key]);
-              if (Object.keys(updateOp[key]).length === 0) {
+              if (utils.hasOwnKeys(updateOp[key]) === false) {
                 delete updateOp[key];
                 update.$unset = update.$unset || {};
                 update.$unset[key] = 1;
@@ -1146,25 +1146,16 @@ Model.createCollection = async function createCollection(options) {
     throw err;
   });
 
-  const collectionOptions = this &&
-    this.schema &&
-    this.schema.options &&
-    this.schema.options.collectionOptions;
+  const collectionOptions = this?.schema?.options?.collectionOptions;
   if (collectionOptions != null) {
     options = Object.assign({}, collectionOptions, options);
   }
 
-  const schemaCollation = this &&
-    this.schema &&
-    this.schema.options &&
-    this.schema.options.collation;
+  const schemaCollation = this?.schema?.options?.collation;
   if (schemaCollation != null) {
     options = Object.assign({ collation: schemaCollation }, options);
   }
-  const capped = this &&
-    this.schema &&
-    this.schema.options &&
-    this.schema.options.capped;
+  const capped = this?.schema?.options?.capped;
   if (capped != null) {
     if (typeof capped === 'number') {
       options = Object.assign({ capped: true, size: capped }, options);
@@ -1172,10 +1163,7 @@ Model.createCollection = async function createCollection(options) {
       options = Object.assign({ capped: true }, capped, options);
     }
   }
-  const timeseries = this &&
-    this.schema &&
-    this.schema.options &&
-    this.schema.options.timeseries;
+  const timeseries = this?.schema?.options?.timeseries;
   if (timeseries != null) {
     options = Object.assign({ timeseries }, options);
     if (options.expireAfterSeconds != null) {
@@ -1190,10 +1178,7 @@ Model.createCollection = async function createCollection(options) {
     }
   }
 
-  const clusteredIndex = this &&
-    this.schema &&
-    this.schema.options &&
-    this.schema.options.clusteredIndex;
+  const clusteredIndex = this?.schema?.options?.clusteredIndex;
   if (clusteredIndex != null) {
     options = Object.assign({ clusteredIndex: { ...clusteredIndex, unique: true } }, options);
   }
@@ -3977,7 +3962,7 @@ Model.updateOne = function updateOne(conditions, doc, options) {
 Model.replaceOne = function replaceOne(conditions, doc, options) {
   _checkContext(this, 'replaceOne');
 
-  const versionKey = this && this.schema && this.schema.options && this.schema.options.versionKey || null;
+  const versionKey = this?.schema?.options?.versionKey || null;
   if (versionKey && !doc[versionKey]) {
     doc[versionKey] = 0;
   }
@@ -4003,10 +3988,7 @@ function _update(model, op, conditions, doc, options) {
   }
   options = typeof options === 'function' ? options : clone(options);
 
-  const versionKey = model &&
-  model.schema &&
-  model.schema.options &&
-  model.schema.options.versionKey || null;
+  const versionKey = model?.schema?.options?.versionKey || null;
   decorateUpdateWithVersionKey(doc, options, versionKey);
 
   return mq[op](conditions, doc, options);
@@ -4986,7 +4968,7 @@ Model._applyQueryMiddleware = function _applyQueryMiddleware() {
       return !!contexts.query;
     }
     if (hook.name === 'deleteOne' || hook.name === 'updateOne') {
-      return !!contexts.query || Object.keys(contexts).length === 0;
+      return !!contexts.query || utils.hasOwnKeys(contexts) === false;
     }
     if (hook.query != null || hook.document != null) {
       return !!hook.query;
diff --git a/lib/mongoose.js b/lib/mongoose.js
index 864b686dd55..c20ae51ffb4 100644
--- a/lib/mongoose.js
+++ b/lib/mongoose.js
@@ -309,7 +309,7 @@ Mongoose.prototype.set = function getsetOptions(key, value) {
       if (optionValue && !_mongoose.connection) {
         _createDefaultConnection(_mongoose);
       } else if (optionValue === false && _mongoose.connection && _mongoose.connection[defaultConnectionSymbol]) {
-        if (_mongoose.connection.readyState === STATES.disconnected && Object.keys(_mongoose.connection.models).length === 0) {
+        if (_mongoose.connection.readyState === STATES.disconnected && utils.hasOwnKeys(_mongoose.connection.models) === false) {
           _mongoose.connections.shift();
         }
       }
@@ -605,8 +605,7 @@ Mongoose.prototype.model = function model(name, schema, collection, options) {
     _mongoose.options.overwriteModels :
     options.overwriteModels;
   if (_mongoose.models.hasOwnProperty(name) && options.cache !== false && overwriteModels !== true) {
-    if (originalSchema &&
-        originalSchema.instanceOfSchema &&
+    if (originalSchema?.instanceOfSchema &&
         originalSchema !== _mongoose.models[name].schema) {
       throw new _mongoose.Error.OverwriteModelError(name);
     }
diff --git a/lib/plugins/trackTransaction.js b/lib/plugins/trackTransaction.js
index 857caac6044..1a45b572b1a 100644
--- a/lib/plugins/trackTransaction.js
+++ b/lib/plugins/trackTransaction.js
@@ -44,7 +44,7 @@ function _getAtomics(doc, previous) {
         utils.isMongooseDocumentArray(val) &&
         val.length &&
         val[arrayAtomicsSymbol] != null &&
-        Object.keys(val[arrayAtomicsSymbol]).length !== 0) {
+        utils.hasOwnKeys(val[arrayAtomicsSymbol])) {
       const existing = previous.get(path) || {};
       pathToAtomics.set(path, mergeAtomics(existing, val[arrayAtomicsSymbol]));
     }
@@ -55,7 +55,7 @@ function _getAtomics(doc, previous) {
     const path = dirt.path;
 
     const val = dirt.value;
-    if (val != null && val[arrayAtomicsSymbol] != null && Object.keys(val[arrayAtomicsSymbol]).length !== 0) {
+    if (val != null && val[arrayAtomicsSymbol] != null && utils.hasOwnKeys(val[arrayAtomicsSymbol])) {
       const existing = previous.get(path) || {};
       pathToAtomics.set(path, mergeAtomics(existing, val[arrayAtomicsSymbol]));
     }
diff --git a/lib/query.js b/lib/query.js
index 57bc291340f..9910a8c16cc 100644
--- a/lib/query.js
+++ b/lib/query.js
@@ -156,10 +156,7 @@ function Query(conditions, options, model, collection) {
   // versions of MongoDB
   this.$useProjection = true;
 
-  const collation = this &&
-    this.schema &&
-    this.schema.options &&
-    this.schema.options.collation || null;
+  const collation = this?.schema?.options?.collation || null;
   if (collation != null) {
     this.options.collation = collation;
   }
@@ -169,7 +166,7 @@ function Query(conditions, options, model, collection) {
 function isEmptyFilter(obj) {
   if (obj == null) return true;
   if (typeof obj !== 'object') return true;
-  if (Object.keys(obj).length === 0) return true;
+  if (utils.hasOwnKeys(obj) === false) return true;
 
   // Check $and, $or, $nor arrays
   for (const key of ['$and', '$or', '$nor']) {
@@ -457,8 +454,8 @@ Query.prototype.clone = function() {
  * @api public
  */
 
-Query.prototype.slice = function() {
-  if (arguments.length === 0) {
+Query.prototype.slice = function(...args) {
+  if (args.length === 0) {
     return this;
   }
 
@@ -467,8 +464,8 @@ Query.prototype.slice = function() {
   let path;
   let val;
 
-  if (arguments.length === 1) {
-    const arg = arguments[0];
+  if (args.length === 1) {
+    const arg = args[0];
     if (typeof arg === 'object' && !Array.isArray(arg)) {
       const keys = Object.keys(arg);
       const numKeys = keys.length;
@@ -479,19 +476,19 @@ Query.prototype.slice = function() {
     }
     this._ensurePath('slice');
     path = this._path;
-    val = arguments[0];
-  } else if (arguments.length === 2) {
-    if ('number' === typeof arguments[0]) {
+    val = args[0];
+  } else if (args.length === 2) {
+    if ('number' === typeof args[0]) {
       this._ensurePath('slice');
       path = this._path;
-      val = [arguments[0], arguments[1]];
+      val = [args[0], args[1]];
     } else {
-      path = arguments[0];
-      val = arguments[1];
+      path = args[0];
+      val = args[1];
     }
-  } else if (arguments.length === 3) {
-    path = arguments[0];
-    val = [arguments[1], arguments[2]];
+  } else if (args.length === 3) {
+    path = args[0];
+    val = [args[1], args[2]];
   }
 
   const p = {};
@@ -2006,7 +2003,7 @@ Query.prototype._fieldsForExec = function() {
   if (this._fields == null) {
     return null;
   }
-  if (Object.keys(this._fields).length === 0) {
+  if (utils.hasOwnKeys(this._fields) === false) {
     return null;
   }
   return clone(this._fields);
@@ -2104,10 +2101,7 @@ Query.prototype._optionsForExec = function(model) {
     options.session = asyncLocalStorage.session;
   }
 
-  const readPreference = model &&
-  model.schema &&
-  model.schema.options &&
-  model.schema.options.read;
+  const readPreference = model?.schema?.options?.read;
   if (!('readPreference' in options) && readPreference) {
     options.readPreference = readPreference;
   }
@@ -2413,13 +2407,15 @@ Query.prototype._find = async function _find() {
   const mongooseOptions = this._mongooseOptions;
   const userProvidedFields = this._userProvidedFields || {};
 
-  applyGlobalMaxTimeMS(this.options, this.model.db.options, this.model.base.options);
-  applyGlobalDiskUse(this.options, this.model.db.options, this.model.base.options);
+  const dbOptions = this.model.db.options;
+  const baseOptions = this.model.base.options;
+  applyGlobalMaxTimeMS(this.options, dbOptions, baseOptions);
+  applyGlobalDiskUse(this.options, dbOptions, baseOptions);
 
   // Separate options to pass down to `completeMany()` in case we need to
   // set a session on the document
   const completeManyOptions = {
-    session: this && this.options && this.options.session || null,
+    session: this?.options?.session || null,
     lean: mongooseOptions.lean || null
   };
 
@@ -2712,8 +2708,10 @@ Query.prototype._findOne = async function _findOne() {
     throw err;
   }
 
-  applyGlobalMaxTimeMS(this.options, this.model.db.options, this.model.base.options);
-  applyGlobalDiskUse(this.options, this.model.db.options, this.model.base.options);
+  const dbOptions = this.model.db.options;
+  const baseOptions = this.model.base.options;
+  applyGlobalMaxTimeMS(this.options, dbOptions, baseOptions);
+  applyGlobalDiskUse(this.options, dbOptions, baseOptions);
 
   const options = this._optionsForExec();
 
@@ -2808,8 +2806,10 @@ Query.prototype._countDocuments = async function _countDocuments() {
     throw this.error();
   }
 
-  applyGlobalMaxTimeMS(this.options, this.model.db.options, this.model.base.options);
-  applyGlobalDiskUse(this.options, this.model.db.options, this.model.base.options);
+  const dbOptions = this.model.db.options;
+  const baseOptions = this.model.base.options;
+  applyGlobalMaxTimeMS(this.options, dbOptions, baseOptions);
+  applyGlobalDiskUse(this.options, dbOptions, baseOptions);
 
   const options = this._optionsForExec();
 
@@ -2836,7 +2836,7 @@ Query.prototype._applyTranslateAliases = function _applyTranslateAliases() {
     return;
   }
 
-  if (this.model?.schema?.aliases && Object.keys(this.model.schema.aliases).length > 0) {
+  if (this.model?.schema?.aliases && utils.hasOwnKeys(this.model.schema.aliases)) {
     this.model.translateAliases(this._conditions, true);
     this.model.translateAliases(this._fields, true);
     this.model.translateAliases(this._update, true);
@@ -2974,8 +2974,10 @@ Query.prototype.__distinct = async function __distinct() {
     throw this.error();
   }
 
-  applyGlobalMaxTimeMS(this.options, this.model.db.options, this.model.base.options);
-  applyGlobalDiskUse(this.options, this.model.db.options, this.model.base.options);
+  const dbOptions = this.model.db.options;
+  const baseOptions = this.model.base.options;
+  applyGlobalMaxTimeMS(this.options, dbOptions, baseOptions);
+  applyGlobalDiskUse(this.options, dbOptions, baseOptions);
 
   const options = this._optionsForExec();
 
@@ -3492,8 +3494,10 @@ Query.prototype._findOneAndUpdate = async function _findOneAndUpdate() {
     throw this.error();
   }
 
-  applyGlobalMaxTimeMS(this.options, this.model.db.options, this.model.base.options);
-  applyGlobalDiskUse(this.options, this.model.db.options, this.model.base.options);
+  const dbOptions = this.model.db.options;
+  const baseOptions = this.model.base.options;
+  applyGlobalMaxTimeMS(this.options, dbOptions, baseOptions);
+  applyGlobalDiskUse(this.options, dbOptions, baseOptions);
 
   if ('strict' in this.options) {
     this._mongooseOptions.strict = this.options.strict;
@@ -3509,7 +3513,7 @@ Query.prototype._findOneAndUpdate = async function _findOneAndUpdate() {
   this._update = setDefaultsOnInsert(this._conditions, this.model.schema,
     this._update, _opts);
 
-  if (!this._update || Object.keys(this._update).length === 0) {
+  if (!this._update || utils.hasOwnKeys(this._update) === false) {
     if (options.upsert) {
       // still need to do the upsert to empty doc
       const $set = clone(this._update);
@@ -3526,7 +3530,7 @@ Query.prototype._findOneAndUpdate = async function _findOneAndUpdate() {
     // In order to make MongoDB 2.6 happy (see
     // https://jira.mongodb.org/browse/SERVER-12266 and related issues)
     // if we have an actual update document but $set is empty, junk the $set.
-    if (this._update.$set && Object.keys(this._update.$set).length === 0) {
+    if (this._update.$set && utils.hasOwnKeys(this._update.$set) === false) {
       delete this._update.$set;
     }
   }
@@ -4015,7 +4019,7 @@ Query.prototype._mergeUpdate = function(update) {
     this._update = Array.isArray(update) ? [] : {};
   }
 
-  if (update == null || (typeof update === 'object' && Object.keys(update).length === 0)) {
+  if (update == null || (typeof update === 'object' && utils.hasOwnKeys(update) === false)) {
     return;
   }
 
@@ -4067,7 +4071,7 @@ async function _updateThunk(op) {
   } else {
     this._update = this._castUpdate(this._update);
 
-    if (this._update == null || Object.keys(this._update).length === 0) {
+    if (this._update == null || utils.hasOwnKeys(this._update) === false) {
       return { acknowledged: false };
     }
 
@@ -4888,8 +4892,7 @@ Query.prototype._castUpdate = function _castUpdate(obj) {
  * @api public
  */
 
-Query.prototype.populate = function() {
-  const args = Array.from(arguments);
+Query.prototype.populate = function(...args) {
   // Bail when given no truthy arguments
   if (!args.some(Boolean)) {
     return this;
@@ -4902,7 +4905,7 @@ Query.prototype.populate = function() {
   if (opts.lean != null) {
     const lean = opts.lean;
     for (const populateOptions of res) {
-      if ((populateOptions && populateOptions.options && populateOptions.options.lean) == null) {
+      if (populateOptions?.options?.lean == null) {
         populateOptions.options = populateOptions.options || {};
         populateOptions.options.lean = lean;
       }
diff --git a/lib/queryHelpers.js b/lib/queryHelpers.js
index 9cb2f546756..4681023f496 100644
--- a/lib/queryHelpers.js
+++ b/lib/queryHelpers.js
@@ -30,11 +30,11 @@ exports.preparePopulationOptionsMQ = function preparePopulationOptionsMQ(query,
   // lean options should trickle through all queries
   if (options.lean != null) {
     pop
-      .filter(p => (p && p.options && p.options.lean) == null)
+      .filter(p => p?.options?.lean == null)
       .forEach(makeLean(options.lean));
   }
 
-  const session = query && query.options && query.options.session || null;
+  const session = query?.options?.session || null;
   if (session != null) {
     pop.forEach(path => {
       if (path.options == null) {
@@ -204,10 +204,7 @@ exports.applyPaths = function applyPaths(fields, schema, sanitizeProjection) {
       }
       break;
     case false:
-      if (schema &&
-          schema.paths['_id'] &&
-          schema.paths['_id'].options &&
-          schema.paths['_id'].options.select === false) {
+      if (schema?.paths['_id']?.options?.select === false) {
         fields._id = 0;
       }
 
diff --git a/lib/schema.js b/lib/schema.js
index d62fe80cdb6..8a4ddddf64c 100644
--- a/lib/schema.js
+++ b/lib/schema.js
@@ -722,9 +722,7 @@ Schema.prototype._defaultToObjectOptions = function(json) {
     return this._defaultToObjectOptionsMap[path];
   }
 
-  const baseOptions = this.base &&
-    this.base.options &&
-    this.base.options[path] || {};
+  const baseOptions = this.base?.options?.[path] || {};
   const schemaOptions = this.options[path] || {};
   // merge base default options with Schema's set default options if available.
   // `clone` is necessary here because `utils.options` directly modifies the second input.
@@ -847,7 +845,7 @@ Schema.prototype.add = function add(obj, prefix) {
           schemaType.discriminator(key, val[0].discriminators[key]);
         }
       }
-    } else if (Object.keys(val).length < 1) {
+    } else if (utils.hasOwnKeys(val) === false) {
       // Special-case: {} always interpreted as Mixed path so leaf at this node
       if (prefix) {
         this.nested[prefix.substring(0, prefix.length - 1)] = true;
@@ -862,7 +860,7 @@ Schema.prototype.add = function add(obj, prefix) {
     } else {
       // There IS a bona-fide type key that may also be a POJO
       const _typeDef = val[typeKey];
-      if (isPOJO(_typeDef) && Object.keys(_typeDef).length > 0) {
+      if (isPOJO(_typeDef) && utils.hasOwnKeys(_typeDef)) {
         // If a POJO is the value of a type key, make it a subdocument
         if (prefix) {
           this.nested[prefix.substring(0, prefix.length - 1)] = true;
@@ -965,7 +963,7 @@ Schema.prototype._removeEncryptedField = function _removeEncryptedField(path) {
  * @returns {boolean}
  */
 Schema.prototype._hasEncryptedFields = function _hasEncryptedFields() {
-  return Object.keys(this.encryptedFields).length > 0;
+  return utils.hasOwnKeys(this.encryptedFields);
 };
 
 /**
@@ -1674,7 +1672,7 @@ Schema.prototype.interpretAsType = function(path, obj, options) {
     if (typeof cast === 'string') {
       cast = MongooseTypes[cast.charAt(0).toUpperCase() + cast.substring(1)];
     } else if (utils.isPOJO(castFromTypeKey)) {
-      if (Object.keys(castFromTypeKey).length) {
+      if (utils.hasOwnKeys(castFromTypeKey)) {
         // The `minimize` and `typeKey` options propagate to child schemas
         // declared inline, like `{ arr: [{ val: { $type: String } }] }`.
         // See gh-3560
diff --git a/lib/schema/array.js b/lib/schema/array.js
index 14b60f22ea2..945cc1a90eb 100644
--- a/lib/schema/array.js
+++ b/lib/schema/array.js
@@ -255,9 +255,7 @@ SchemaArray.prototype.checkRequired = function checkRequired(value, doc) {
 SchemaArray.prototype.enum = function() {
   let arr = this;
   while (true) {
-    const instance = arr &&
-    arr.embeddedSchemaType &&
-    arr.embeddedSchemaType.instance;
+    const instance = arr?.embeddedSchemaType?.instance;
     if (instance === 'Array') {
       arr = arr.embeddedSchemaType;
       continue;
diff --git a/lib/schema/map.js b/lib/schema/map.js
index 2ac2a3371a8..e7bf1363f87 100644
--- a/lib/schema/map.js
+++ b/lib/schema/map.js
@@ -172,7 +172,7 @@ SchemaMap.prototype._createNestedSchemaType = function _createNestedSchemaType(s
   let _mapType = { type: {} };
   if (utils.hasUserDefinedProperty(obj, 'of')) {
     const isInlineSchema = utils.isPOJO(obj.of) &&
-      Object.keys(obj.of).length > 0 &&
+      utils.hasOwnKeys(obj.of) &&
       !utils.hasUserDefinedProperty(obj.of, schema.options.typeKey);
     if (isInlineSchema) {
       _mapType = { [schema.options.typeKey]: new Schema(obj.of) };
diff --git a/lib/schema/mixed.js b/lib/schema/mixed.js
index 93740640891..c95a373a9e9 100644
--- a/lib/schema/mixed.js
+++ b/lib/schema/mixed.js
@@ -26,7 +26,7 @@ function SchemaMixed(path, options, _schemaOptions, parentSchema) {
     if (Array.isArray(def) && def.length === 0) {
       // make sure empty array defaults are handled
       options.default = Array;
-    } else if (!options.shared && isObject(def) && Object.keys(def).length === 0) {
+    } else if (!options.shared && isObject(def) && utils.hasOwnKeys(def) === false) {
       // prevent odd "shared" objects between documents
       options.default = function() {
         return {};
diff --git a/lib/schema/number.js b/lib/schema/number.js
index 33d9615fb9f..5e172639380 100644
--- a/lib/schema/number.js
+++ b/lib/schema/number.js
@@ -221,7 +221,7 @@ SchemaNumber.prototype.min = function(value, message) {
     }, this);
   }
 
-  if (value !== null && value !== undefined) {
+  if (value != null) {
     let msg = message || MongooseError.messages.Number.min;
     msg = msg.replace(/{MIN}/, value);
     this.validators.push({
@@ -275,7 +275,7 @@ SchemaNumber.prototype.max = function(value, message) {
     }, this);
   }
 
-  if (value !== null && value !== undefined) {
+  if (value != null) {
     let msg = message || MongooseError.messages.Number.max;
     msg = msg.replace(/{MAX}/, value);
     this.validators.push({
diff --git a/lib/schema/string.js b/lib/schema/string.js
index fbc88b38c02..7197bc0e103 100644
--- a/lib/schema/string.js
+++ b/lib/schema/string.js
@@ -416,7 +416,7 @@ SchemaString.prototype.minlength = function(value, message) {
     }, this);
   }
 
-  if (value !== null && value !== undefined) {
+  if (value != null) {
     let msg = message || MongooseError.messages.String.minlength;
     msg = msg.replace(/{MINLENGTH}/, value);
     this.validators.push({
@@ -472,7 +472,7 @@ SchemaString.prototype.maxlength = function(value, message) {
     }, this);
   }
 
-  if (value !== null && value !== undefined) {
+  if (value != null) {
     let msg = message || MongooseError.messages.String.maxlength;
     msg = msg.replace(/{MAXLENGTH}/, value);
     this.validators.push({
diff --git a/lib/schema/subdocument.js b/lib/schema/subdocument.js
index dcc42327e5b..64975f724d6 100644
--- a/lib/schema/subdocument.js
+++ b/lib/schema/subdocument.js
@@ -41,8 +41,7 @@ function SchemaSubdocument(schema, path, options, parentSchema) {
   if (schema.options.timeseries) {
     throw new InvalidSchemaOptionError(path, 'timeseries');
   }
-  const schemaTypeIdOption = SchemaSubdocument.defaultOptions &&
-    SchemaSubdocument.defaultOptions._id;
+  const schemaTypeIdOption = SchemaSubdocument.defaultOptions?._id;
   if (schemaTypeIdOption != null) {
     options = options || {};
     options._id = schemaTypeIdOption;
@@ -216,7 +215,7 @@ SchemaSubdocument.prototype.cast = function(val, doc, init, priorVal, options) {
     applyDefaults(subdoc, selected, exclude);
   } else {
     options = Object.assign({}, options, { priorDoc: priorVal });
-    if (Object.keys(val).length === 0) {
+    if (utils.hasOwnKeys(val) === false) {
       return new Constructor({}, selected, doc, options);
     }
 
diff --git a/lib/schemaType.js b/lib/schemaType.js
index 063c5b73047..a30f90cdeca 100644
--- a/lib/schemaType.js
+++ b/lib/schemaType.js
@@ -1209,7 +1209,7 @@ SchemaType.prototype.getDefault = function(scope, init, options) {
     ret = this.defaultValue;
   }
 
-  if (ret !== null && ret !== undefined) {
+  if (ret != null) {
     if (typeof ret === 'object' && (!this.options || !this.options.shared)) {
       ret = clone(ret);
     }
diff --git a/lib/types/array/index.js b/lib/types/array/index.js
index b21c23bfd12..19f37cfd039 100644
--- a/lib/types/array/index.js
+++ b/lib/types/array/index.js
@@ -85,7 +85,7 @@ function MongooseArray(values, path, doc, schematype) {
       if (mongooseArrayMethods.hasOwnProperty(prop)) {
         return mongooseArrayMethods[prop];
       }
-      if (schematype && schematype.virtuals && schematype.virtuals.hasOwnProperty(prop)) {
+      if (schematype?.virtuals?.hasOwnProperty(prop)) {
         return schematype.virtuals[prop].applyGetters(undefined, target);
       }
       if (typeof prop === 'string' && numberRE.test(prop) && schematype?.embeddedSchemaType != null) {
@@ -99,7 +99,7 @@ function MongooseArray(values, path, doc, schematype) {
         mongooseArrayMethods.set.call(proxy, prop, value, false);
       } else if (internals.hasOwnProperty(prop)) {
         internals[prop] = value;
-      } else if (schematype && schematype.virtuals && schematype.virtuals.hasOwnProperty(prop)) {
+      } else if (schematype?.virtuals?.hasOwnProperty(prop)) {
         schematype.virtuals[prop].applySetters(value, target);
       } else {
         __array[prop] = value;
diff --git a/lib/types/array/methods/index.js b/lib/types/array/methods/index.js
index 46fe80815b8..a14cf16fcf3 100644
--- a/lib/types/array/methods/index.js
+++ b/lib/types/array/methods/index.js
@@ -338,7 +338,7 @@ const methods = {
 
     // check for impossible $atomic combos (Mongo denies more than one
     // $atomic op on a single path
-    if (atomics.$set || Object.keys(atomics).length && !(op in atomics)) {
+    if (atomics.$set || utils.hasOwnKeys(atomics) && !(op in atomics)) {
       // a different op was previously registered.
       // save the entire thing.
       this[arrayAtomicsSymbol] = { $set: this };
@@ -995,7 +995,7 @@ function _minimizePath(obj, parts, i) {
   }
 
   _minimizePath(obj[parts[0]], parts, i + 1);
-  if (obj[parts[0]] != null && typeof obj[parts[0]] === 'object' && Object.keys(obj[parts[0]]).length === 0) {
+  if (obj[parts[0]] != null && typeof obj[parts[0]] === 'object' && utils.hasOwnKeys(obj[parts[0]]) === false) {
     delete obj[parts[0]];
   }
 }
diff --git a/lib/types/documentArray/index.js b/lib/types/documentArray/index.js
index ccc0d230fdb..0fd138757db 100644
--- a/lib/types/documentArray/index.js
+++ b/lib/types/documentArray/index.js
@@ -79,7 +79,7 @@ function MongooseDocumentArray(values, path, doc, schematype) {
       if (DocumentArrayMethods.hasOwnProperty(prop)) {
         return DocumentArrayMethods[prop];
       }
-      if (schematype && schematype.virtuals && schematype.virtuals.hasOwnProperty(prop)) {
+      if (schematype?.virtuals?.hasOwnProperty(prop)) {
         return schematype.virtuals[prop].applyGetters(undefined, target);
       }
       if (ArrayMethods.hasOwnProperty(prop)) {
@@ -93,7 +93,7 @@ function MongooseDocumentArray(values, path, doc, schematype) {
         DocumentArrayMethods.set.call(proxy, prop, value, false);
       } else if (internals.hasOwnProperty(prop)) {
         internals[prop] = value;
-      } else if (schematype && schematype.virtuals && schematype.virtuals.hasOwnProperty(prop)) {
+      } else if (schematype?.virtuals?.hasOwnProperty(prop)) {
         schematype.virtuals[prop].applySetters(value, target);
       } else {
         __array[prop] = value;
diff --git a/lib/types/documentArray/methods/index.js b/lib/types/documentArray/methods/index.js
index b17a31d0638..435725a95c6 100644
--- a/lib/types/documentArray/methods/index.js
+++ b/lib/types/documentArray/methods/index.js
@@ -65,7 +65,7 @@ const methods = {
       value instanceof Constructor;
     if (isInstance ||
         // Hack re: #5001, see #5005
-        (value && value.constructor && value.constructor.baseCasterConstructor === Constructor)) {
+        value?.constructor?.baseCasterConstructor === Constructor) {
       if (!(value[documentArrayParent] && value.__parentArray)) {
         // value may have been created using array.create()
         value[documentArrayParent] = this[arrayParentSymbol];
@@ -133,9 +133,9 @@ const methods = {
     const schemaType = this[arraySchemaSymbol];
     let idSchemaType = null;
 
-    if (schemaType && schemaType.schema) {
+    if (schemaType?.schema) {
       idSchemaType = schemaType.schema.path('_id');
-    } else if (schemaType && schemaType.casterConstructor && schemaType.casterConstructor.schema) {
+    } else if (schemaType?.casterConstructor?.schema) {
       idSchemaType = schemaType.casterConstructor.schema.path('_id');
     }
 
diff --git a/lib/types/subdocument.js b/lib/types/subdocument.js
index 5d39e1c214e..89d06fcaaf3 100644
--- a/lib/types/subdocument.js
+++ b/lib/types/subdocument.js
@@ -422,7 +422,7 @@ Subdocument.prototype.$toObject = function $toObject(options, json) {
 
   // If `$toObject()` was called recursively, respect the minimize option, including schematype level minimize.
   // If minimize is set, then we can minimize out the whole object.
-  if (Object.keys(ret).length === 0 && options?._calledWithOptions != null) {
+  if (utils.hasOwnKeys(ret) === false && options?._calledWithOptions != null) {
     const minimize = options._calledWithOptions?.minimize ?? this?.$__schemaTypeOptions?.minimize ?? options.minimize;
     if (minimize && !this.constructor.$__required) {
       return undefined;
diff --git a/lib/utils.js b/lib/utils.js
index 2b896dce28b..217c63906bc 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -436,10 +436,26 @@ exports.isNativeObject = function(arg) {
  * @param {Any} val
  */
 
-exports.isEmptyObject = function(val) {
-  return val != null &&
-    typeof val === 'object' &&
-    Object.keys(val).length === 0;
+exports.isEmptyObject = function isEmptyObject(val) {
+  if (val == null || typeof val !== 'object') {
+    return false;
+  }
+  return exports.hasOwnKeys(val) === false;
+};
+
+/**
+ * Determines if `obj` has any own keys. Assumes obj is already an object.
+ * Faster than Object.keys(obj).length > 0.
+ * @param {Object} obj
+ */
+
+exports.hasOwnKeys = function hasOwnKeys(obj) {
+  for (const key in obj) {
+    if (Object.prototype.hasOwnProperty.call(obj, key)) {
+      return true;
+    }
+  }
+  return false;
 };
 
 /**