diff --git a/server/src/main/java/org/elasticsearch/common/TimeBasedUUIDGenerator.java b/server/src/main/java/org/elasticsearch/common/TimeBasedUUIDGenerator.java
index c30a8d0aaa2..f053d3ecaf7 100644
--- a/server/src/main/java/org/elasticsearch/common/TimeBasedUUIDGenerator.java
+++ b/server/src/main/java/org/elasticsearch/common/TimeBasedUUIDGenerator.java
@@ -21,6 +21,7 @@ package org.elasticsearch.common;
 
 import java.util.Base64;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 
 /**
  * These are essentially flake ids but we use 6 (not 8) bytes for timestamp, and use 3 (not 2) bytes for sequence number. We also reorder
@@ -37,7 +38,7 @@ class TimeBasedUUIDGenerator implements UUIDGenerator {
     private final AtomicInteger sequenceNumber = new AtomicInteger(SecureRandomHolder.INSTANCE.nextInt());
 
     // Used to ensure clock moves forward:
-    private long lastTimestamp;
+    private final AtomicLong lastTimestamp = new AtomicLong(0);
 
     private static final byte[] SECURE_MUNGED_ADDRESS = MacAddressProvider.getSecureMungedAddress();
 
@@ -58,21 +59,22 @@ class TimeBasedUUIDGenerator implements UUIDGenerator {
     @Override
     public String getBase64UUID()  {
         final int sequenceId = sequenceNumber.incrementAndGet() & 0xffffff;
-        long timestamp = currentTimeMillis();
+        long currentTimeMillis = currentTimeMillis();
 
-        synchronized (this) {
-            // Don't let timestamp go backwards, at least "on our watch" (while this JVM is running).  We are still vulnerable if we are
-            // shut down, clock goes backwards, and we restart... for this we randomize the sequenceNumber on init to decrease chance of
-            // collision:
-            timestamp = Math.max(lastTimestamp, timestamp);
+        long timestamp = this.lastTimestamp.updateAndGet(lastTimestamp -> {
+            // Don't let timestamp go backwards, at least "on our watch" (while this JVM is running).  We are
+            // still vulnerable if we are shut down, clock goes backwards, and we restart... for this we
+            // randomize the sequenceNumber on init to decrease chance of collision:
+            long nonBackwardsTimestamp = Math.max(lastTimestamp, currentTimeMillis);
 
             if (sequenceId == 0) {
-                // Always force the clock to increment whenever sequence number is 0, in case we have a long time-slip backwards:
-                timestamp++;
+                // Always force the clock to increment whenever sequence number is 0, in case we have a long
+                // time-slip backwards:
+                nonBackwardsTimestamp++;
             }
 
-            lastTimestamp = timestamp;
-        }
+            return nonBackwardsTimestamp;
+        });
 
         final byte[] uuidBytes = new byte[15];
         int i = 0;