diff --git a/server/src/main/java/org/elasticsearch/action/resync/ResyncReplicationRequest.java b/server/src/main/java/org/elasticsearch/action/resync/ResyncReplicationRequest.java
index d4e2c652fa8..ca003bfc07b 100644
--- a/server/src/main/java/org/elasticsearch/action/resync/ResyncReplicationRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/resync/ResyncReplicationRequest.java
@@ -19,6 +19,7 @@
 package org.elasticsearch.action.resync;
 
 import org.elasticsearch.Version;
+import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.support.replication.ReplicatedWriteRequest;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -28,6 +29,7 @@ import org.elasticsearch.index.translog.Translog;
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Objects;
 
 /**
  * Represents a batch of operations sent from the primary to its replicas during the primary-replica resync.
@@ -36,15 +38,17 @@ public final class ResyncReplicationRequest extends ReplicatedWriteRequest<Resyn
 
     private long trimAboveSeqNo;
     private Translog.Operation[] operations;
+    private long maxSeenAutoIdTimestampOnPrimary;
 
     ResyncReplicationRequest() {
         super();
     }
 
-    public ResyncReplicationRequest(final ShardId shardId, final long trimAboveSeqNo,
-                                    final Translog.Operation[] operations) {
+    public ResyncReplicationRequest(final ShardId shardId, final long trimAboveSeqNo, final long maxSeenAutoIdTimestampOnPrimary,
+                                    final Translog.Operation[]operations) {
         super(shardId);
         this.trimAboveSeqNo = trimAboveSeqNo;
+        this.maxSeenAutoIdTimestampOnPrimary = maxSeenAutoIdTimestampOnPrimary;
         this.operations = operations;
     }
 
@@ -52,6 +56,10 @@ public final class ResyncReplicationRequest extends ReplicatedWriteRequest<Resyn
         return trimAboveSeqNo;
     }
 
+    public long getMaxSeenAutoIdTimestampOnPrimary() {
+        return maxSeenAutoIdTimestampOnPrimary;
+    }
+
     public Translog.Operation[] getOperations() {
         return operations;
     }
@@ -73,6 +81,11 @@ public final class ResyncReplicationRequest extends ReplicatedWriteRequest<Resyn
         } else {
             trimAboveSeqNo = SequenceNumbers.UNASSIGNED_SEQ_NO;
         }
+        if (in.getVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+            maxSeenAutoIdTimestampOnPrimary = in.readZLong();
+        } else {
+            maxSeenAutoIdTimestampOnPrimary = IndexRequest.UNSET_AUTO_GENERATED_TIMESTAMP;
+        }
         operations = in.readArray(Translog.Operation::readOperation, Translog.Operation[]::new);
     }
 
@@ -82,6 +95,9 @@ public final class ResyncReplicationRequest extends ReplicatedWriteRequest<Resyn
         if (out.getVersion().onOrAfter(Version.V_6_4_0)) {
             out.writeZLong(trimAboveSeqNo);
         }
+        if (out.getVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+            out.writeZLong(maxSeenAutoIdTimestampOnPrimary);
+        }
         out.writeArray(Translog.Operation::writeOperation, operations);
     }
 
@@ -90,13 +106,13 @@ public final class ResyncReplicationRequest extends ReplicatedWriteRequest<Resyn
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
         final ResyncReplicationRequest that = (ResyncReplicationRequest) o;
-        return trimAboveSeqNo == that.trimAboveSeqNo
+        return trimAboveSeqNo == that.trimAboveSeqNo && maxSeenAutoIdTimestampOnPrimary == that.maxSeenAutoIdTimestampOnPrimary
             && Arrays.equals(operations, that.operations);
     }
 
     @Override
     public int hashCode() {
-        return Long.hashCode(trimAboveSeqNo) + 31 * Arrays.hashCode(operations);
+        return Objects.hash(trimAboveSeqNo, maxSeenAutoIdTimestampOnPrimary, operations);
     }
 
     @Override
@@ -106,6 +122,7 @@ public final class ResyncReplicationRequest extends ReplicatedWriteRequest<Resyn
             ", timeout=" + timeout +
             ", index='" + index + '\'' +
             ", trimAboveSeqNo=" + trimAboveSeqNo +
+            ", maxSeenAutoIdTimestampOnPrimary=" + maxSeenAutoIdTimestampOnPrimary +
             ", ops=" + operations.length +
             "}";
     }
diff --git a/server/src/main/java/org/elasticsearch/action/resync/TransportResyncReplicationAction.java b/server/src/main/java/org/elasticsearch/action/resync/TransportResyncReplicationAction.java
index 7881e57200b..6d0c35345b1 100644
--- a/server/src/main/java/org/elasticsearch/action/resync/TransportResyncReplicationAction.java
+++ b/server/src/main/java/org/elasticsearch/action/resync/TransportResyncReplicationAction.java
@@ -119,6 +119,12 @@ public class TransportResyncReplicationAction extends TransportWriteAction<Resyn
 
     public static Translog.Location performOnReplica(ResyncReplicationRequest request, IndexShard replica) throws Exception {
         Translog.Location location = null;
+        /*
+         * Operations received from resync do not have auto_id_timestamp individually, we need to bootstrap this max_seen_timestamp
+         * (at least the highest timestamp from any of these operations) to make sure that we will disable optimization for the same
+         * append-only requests with timestamp (sources of these operations) that are replicated; otherwise we may have duplicates.
+         */
+        replica.updateMaxUnsafeAutoIdTimestamp(request.getMaxSeenAutoIdTimestampOnPrimary());
         for (Translog.Operation operation : request.getOperations()) {
             final Engine.Result operationResult = replica.applyTranslogOperation(operation, Engine.Operation.Origin.REPLICA);
             if (operationResult.getResultType() == Engine.Result.Type.MAPPING_UPDATE_REQUIRED) {
diff --git a/server/src/main/java/org/elasticsearch/index/shard/PrimaryReplicaSyncer.java b/server/src/main/java/org/elasticsearch/index/shard/PrimaryReplicaSyncer.java
index 016a8afff69..3530fe5ae5d 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/PrimaryReplicaSyncer.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/PrimaryReplicaSyncer.java
@@ -135,9 +135,11 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
                     }
                 }
             };
-
+            // We must capture the timestamp after snapshotting a snapshot of operations to make sure
+            // that the auto_id_timestamp of every operation in the snapshot is at most this value.
+            final long maxSeenAutoIdTimestamp = indexShard.getMaxSeenAutoIdTimestamp();
             resync(shardId, indexShard.routingEntry().allocationId().getId(), indexShard.getPendingPrimaryTerm(), wrappedSnapshot,
-                startingSeqNo, maxSeqNo, resyncListener);
+                startingSeqNo, maxSeqNo, maxSeenAutoIdTimestamp, resyncListener);
         } catch (Exception e) {
             try {
                 IOUtils.close(snapshot);
@@ -150,7 +152,7 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
     }
 
     private void resync(final ShardId shardId, final String primaryAllocationId, final long primaryTerm, final Translog.Snapshot snapshot,
-                        long startingSeqNo, long maxSeqNo, ActionListener<ResyncTask> listener) {
+                        long startingSeqNo, long maxSeqNo, long maxSeenAutoIdTimestamp, ActionListener<ResyncTask> listener) {
         ResyncRequest request = new ResyncRequest(shardId, primaryAllocationId);
         ResyncTask resyncTask = (ResyncTask) taskManager.register("transport", "resync", request); // it's not transport :-)
         ActionListener<Void> wrappedListener = new ActionListener<Void>() {
@@ -170,7 +172,7 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
         };
         try {
             new SnapshotSender(logger, syncAction, resyncTask, shardId, primaryAllocationId, primaryTerm, snapshot, chunkSize.bytesAsInt(),
-                startingSeqNo, maxSeqNo, wrappedListener).run();
+                startingSeqNo, maxSeqNo, maxSeenAutoIdTimestamp, wrappedListener).run();
         } catch (Exception e) {
             wrappedListener.onFailure(e);
         }
@@ -191,6 +193,7 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
         private final Translog.Snapshot snapshot;
         private final long startingSeqNo;
         private final long maxSeqNo;
+        private final long maxSeenAutoIdTimestamp;
         private final int chunkSizeInBytes;
         private final ActionListener<Void> listener;
         private final AtomicBoolean firstMessage = new AtomicBoolean(true);
@@ -199,7 +202,8 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
         private AtomicBoolean closed = new AtomicBoolean();
 
         SnapshotSender(Logger logger, SyncAction syncAction, ResyncTask task, ShardId shardId, String primaryAllocationId, long primaryTerm,
-                       Translog.Snapshot snapshot, int chunkSizeInBytes, long startingSeqNo, long maxSeqNo, ActionListener<Void> listener) {
+                       Translog.Snapshot snapshot, int chunkSizeInBytes, long startingSeqNo, long maxSeqNo,
+                       long maxSeenAutoIdTimestamp, ActionListener<Void> listener) {
             this.logger = logger;
             this.syncAction = syncAction;
             this.task = task;
@@ -210,6 +214,7 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
             this.chunkSizeInBytes = chunkSizeInBytes;
             this.startingSeqNo = startingSeqNo;
             this.maxSeqNo = maxSeqNo;
+            this.maxSeenAutoIdTimestamp = maxSeenAutoIdTimestamp;
             this.listener = listener;
             task.setTotalOperations(snapshot.totalOperations());
         }
@@ -260,7 +265,7 @@ public class PrimaryReplicaSyncer extends AbstractComponent {
             if (!operations.isEmpty() || trimmedAboveSeqNo != SequenceNumbers.UNASSIGNED_SEQ_NO) {
                 task.setPhase("sending_ops");
                 ResyncReplicationRequest request =
-                    new ResyncReplicationRequest(shardId, trimmedAboveSeqNo, operations.toArray(EMPTY_ARRAY));
+                    new ResyncReplicationRequest(shardId, trimmedAboveSeqNo, maxSeenAutoIdTimestamp, operations.toArray(EMPTY_ARRAY));
                 logger.trace("{} sending batch of [{}][{}] (total sent: [{}], skipped: [{}])", shardId, operations.size(),
                     new ByteSizeValue(size), totalSentOps.get(), totalSkippedOps.get());
                 firstMessage.set(false);
diff --git a/server/src/test/java/org/elasticsearch/action/resync/ResyncReplicationRequestTests.java b/server/src/test/java/org/elasticsearch/action/resync/ResyncReplicationRequestTests.java
index 15b8e1c99d2..230eccb0578 100644
--- a/server/src/test/java/org/elasticsearch/action/resync/ResyncReplicationRequestTests.java
+++ b/server/src/test/java/org/elasticsearch/action/resync/ResyncReplicationRequestTests.java
@@ -38,7 +38,7 @@ public class ResyncReplicationRequestTests extends ESTestCase {
         final Translog.Index index = new Translog.Index("type", "id", 0, randomNonNegativeLong(),
             randomNonNegativeLong(), bytes, null, -1);
         final ShardId shardId = new ShardId(new Index("index", "uuid"), 0);
-        final ResyncReplicationRequest before = new ResyncReplicationRequest(shardId, 42L, new Translog.Operation[]{index});
+        final ResyncReplicationRequest before = new ResyncReplicationRequest(shardId, 42L, 100, new Translog.Operation[]{index});
 
         final BytesStreamOutput out = new BytesStreamOutput();
         before.writeTo(out);
diff --git a/server/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java b/server/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java
index 3883554acc0..c38fb8a4956 100644
--- a/server/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java
+++ b/server/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java
@@ -22,6 +22,7 @@ package org.elasticsearch.index.replication;
 import org.apache.logging.log4j.Logger;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexableField;
+import org.elasticsearch.Version;
 import org.elasticsearch.action.admin.indices.flush.FlushRequest;
 import org.elasticsearch.action.bulk.BulkShardRequest;
 import org.elasticsearch.action.index.IndexRequest;
@@ -633,6 +634,49 @@ public class RecoveryDuringReplicationTests extends ESIndexLevelReplicationTestC
         }
     }
 
+    public void testTransferMaxSeenAutoIdTimestampOnResync() throws Exception {
+        try (ReplicationGroup shards = createGroup(2)) {
+            shards.startAll();
+            IndexShard primary = shards.getPrimary();
+            IndexShard replica1 = shards.getReplicas().get(0);
+            IndexShard replica2 = shards.getReplicas().get(1);
+            long maxTimestampOnReplica1 = -1;
+            long maxTimestampOnReplica2 = -1;
+            List<IndexRequest> replicationRequests = new ArrayList<>();
+            for (int numDocs = between(1, 10), i = 0; i < numDocs; i++) {
+                final IndexRequest indexRequest = new IndexRequest(index.getName(), "type").source("{}", XContentType.JSON);
+                indexRequest.process(Version.CURRENT, null, index.getName());
+                final IndexRequest copyRequest;
+                if (randomBoolean()) {
+                    copyRequest = copyIndexRequest(indexRequest);
+                    indexRequest.onRetry();
+                } else {
+                    copyRequest = copyIndexRequest(indexRequest);
+                    copyRequest.onRetry();
+                }
+                replicationRequests.add(copyRequest);
+                final BulkShardRequest bulkShardRequest = indexOnPrimary(indexRequest, primary);
+                if (randomBoolean()) {
+                    indexOnReplica(bulkShardRequest, shards, replica1);
+                    maxTimestampOnReplica1 = Math.max(maxTimestampOnReplica1, indexRequest.getAutoGeneratedTimestamp());
+                } else {
+                    indexOnReplica(bulkShardRequest, shards, replica2);
+                    maxTimestampOnReplica2 = Math.max(maxTimestampOnReplica2, indexRequest.getAutoGeneratedTimestamp());
+                }
+            }
+            assertThat(replica1.getMaxSeenAutoIdTimestamp(), equalTo(maxTimestampOnReplica1));
+            assertThat(replica2.getMaxSeenAutoIdTimestamp(), equalTo(maxTimestampOnReplica2));
+            shards.promoteReplicaToPrimary(replica1).get();
+            assertThat(replica2.getMaxSeenAutoIdTimestamp(), equalTo(maxTimestampOnReplica1));
+            for (IndexRequest request : replicationRequests) {
+                shards.index(request); // deliver via normal replication
+            }
+            for (IndexShard shard : shards) {
+                assertThat(shard.getMaxSeenAutoIdTimestamp(), equalTo(Math.max(maxTimestampOnReplica1, maxTimestampOnReplica2)));
+            }
+        }
+    }
+
     public static class BlockingTarget extends RecoveryTarget {
 
         private final CountDownLatch recoveryBlocked;
diff --git a/server/src/test/java/org/elasticsearch/index/shard/PrimaryReplicaSyncerTests.java b/server/src/test/java/org/elasticsearch/index/shard/PrimaryReplicaSyncerTests.java
index c5fc0e4b034..28e625b34df 100644
--- a/server/src/test/java/org/elasticsearch/index/shard/PrimaryReplicaSyncerTests.java
+++ b/server/src/test/java/org/elasticsearch/index/shard/PrimaryReplicaSyncerTests.java
@@ -76,7 +76,7 @@ public class PrimaryReplicaSyncerTests extends IndexShardTestCase {
             // Index doc but not advance local checkpoint.
             shard.applyIndexOperationOnPrimary(Versions.MATCH_ANY, VersionType.INTERNAL,
                 SourceToParse.source(shard.shardId().getIndexName(), "_doc", Integer.toString(i), new BytesArray("{}"), XContentType.JSON),
-                IndexRequest.UNSET_AUTO_GENERATED_TIMESTAMP, false);
+                randomBoolean() ? IndexRequest.UNSET_AUTO_GENERATED_TIMESTAMP : randomNonNegativeLong(), true);
         }
 
         long globalCheckPoint = numDocs > 0 ? randomIntBetween(0, numDocs - 1) : 0;
@@ -105,6 +105,8 @@ public class PrimaryReplicaSyncerTests extends IndexShardTestCase {
                     .findFirst()
                     .isPresent(),
                 is(false));
+
+            assertThat(resyncRequest.getMaxSeenAutoIdTimestampOnPrimary(), equalTo(shard.getMaxSeenAutoIdTimestamp()));
         }
         if (syncNeeded && globalCheckPoint < numDocs - 1) {
             if (shard.indexSettings.isSoftDeleteEnabled()) {