Do not call getRealTimeTopic

services/venice-controller/src/main/java/com/linkedin/venice/controller/VeniceHelixAdmin.java

@@ -3539,7 +3539,8 @@ public Version getReferenceVersionForStreamingWrites(String clusterName, String
          * Create RT topic here in parent region. For child regions, RT should always be created as part of
          * {@link RealTimeTopicSwitcher#ensurePreconditions(PubSubTopic, PubSubTopic, Store, Optional)}
          */
-        getRealTimeTopic(clusterName, storeName, partitionCount);
+        // getRealTimeTopic(clusterName, storeName, partitionCount);
+        System.out.println("getRealTimeTopic");
       }
       PubSubTopic rtTopic = pubSubTopicRepository.getTopic(Version.composeRealTimeTopic(storeName));
       if (!getTopicManager().containsTopicAndAllPartitionsAreOnline(rtTopic, partitionCount)

services/venice-controller/src/main/java/com/linkedin/venice/ingestion/control/RealTimeTopicSwitcher.java

@@ -137,19 +137,10 @@ void ensurePreconditions(
     Version version =
         store.getVersion(Version.parseVersionFromKafkaTopicName(topicWhereToSendTheTopicSwitch.getName()));
     /**
-     * TopicReplicator is used in child fabrics to create real-time (RT) topic when a child fabric
-     * is ready to start buffer replay but RT topic doesn't exist. This scenario could happen for a
-     * hybrid store when users haven't started any Samza job yet. In this case, RT topic should be
-     * created with proper retention time instead of the default 5 days retention.
-     *
-     * Potential race condition: If both rewind-time update operation and buffer-replay
-     * start at the same time, RT topic might not be created with the expected retention time,
-     * which can be fixed by sending another rewind-time update command.
-     *
-     * TODO: RT topic should be created in both parent and child fabrics when the store is converted to
-     *       hybrid (update store command handling). However, if a store is converted to hybrid when it
-     *       doesn't have any existing version or a correct storage quota, we cannot decide the partition
-     *       number for it.
+     * We create the real-time topics when creating hybrid version for the first time. This is to ensure that the
+     * real-time topics are created with the correct partition count. Here we'll only check retention time and update
+     * it if necessary.
+     * TODO: Remove topic creation logic from here once new code is deployed to all regions.
      */
     createRealTimeTopicIfNeeded(store, version, srcTopicName, hybridStoreConfig.get());
     if (version != null && version.isSeparateRealTimeTopicEnabled()) {
@@ -289,7 +280,7 @@ public void switchToRealTimeTopic(
     } else {
       hybridStoreConfig = Optional.ofNullable(store.getHybridStoreConfig());
     }
-    // ensurePreconditions(realTimeTopic, topicWhereToSendTheTopicSwitch, store, hybridStoreConfig);
+    ensurePreconditions(realTimeTopic, topicWhereToSendTheTopicSwitch, store, hybridStoreConfig);
     long rewindStartTimestamp = getRewindStartTime(version, hybridStoreConfig, version.getCreatedTime());
     PubSubTopic finalTopicWhereToSendTheTopicSwitch = version.getPushType().isStreamReprocessing()
         ? pubSubTopicRepository.getTopic(Version.composeStreamReprocessingTopic(store.getName(), version.getNumber()))