address review comments

Author: arjun4084346

clients/da-vinci-client/src/main/java/com/linkedin/davinci/DaVinciBackend.java

@@ -561,6 +561,11 @@ public SubscriptionBasedReadOnlyStoreRepository getStoreRepository() {
     return storeRepository;
   }
 
+  /**
+   * Resolves and returns the store object for the given store name.
+   * For user system stores, this returns the SystemStoreAttributes from the parent user store.
+   * For regular stores and shared system stores, this returns the Store object directly.
+   */
   public final Object getStore(String storeName) {
     VeniceSystemStoreType systemStoreType = VeniceSystemStoreType.getSystemStoreType(storeName);
     if (systemStoreType != null) {

internal/venice-common/src/main/java/com/linkedin/venice/pushstatushelper/PushStatusStoreVeniceWriterCache.java

@@ -1,6 +1,7 @@
 package com.linkedin.venice.pushstatushelper;
 
 import com.linkedin.venice.common.VeniceSystemStoreUtils;
+import com.linkedin.venice.exceptions.VeniceException;
 import com.linkedin.venice.meta.Store;
 import com.linkedin.venice.meta.StoreInfo;
 import com.linkedin.venice.meta.SystemStoreAttributes;
@@ -52,8 +53,10 @@ public VeniceWriter prepareVeniceWriter(String storeName) {
         rtTopic = Utils.getRealTimeTopicName((Store) store);
       } else if (store instanceof StoreInfo) {
         rtTopic = Utils.getRealTimeTopicName((StoreInfo) store);
-      } else {
+      } else if (store instanceof SystemStoreAttributes) {
         rtTopic = Utils.getRealTimeTopicName((SystemStoreAttributes) store);
+      } else {
+        throw new VeniceException("Unexpected store type for: " + storeName + ", type: " + store.getClass().getName());
       }
       VeniceWriterOptions options = new VeniceWriterOptions.Builder(rtTopic)
           .setKeyPayloadSerializer(

internal/venice-common/src/main/java/com/linkedin/venice/system/store/MetaStoreWriter.java

@@ -79,7 +79,10 @@ public class MetaStoreWriter implements Closeable {
   private final PubSubTopicRepository pubSubTopicRepository;
   private final long closeTimeoutMs;
   private final int numOfConcurrentVwCloseOps;
-
+  /*
+   * Function to resolve store names to Store objects. Used to fetch system store metadata
+   * for determining the correct RT topic names.
+   */
   public Function<String, Store> storeResolver;
 
   public MetaStoreWriter(
@@ -372,8 +375,10 @@ VeniceWriter getOrCreateMetaStoreWriter(String metaStoreName) {
       int largestUsedRTVersionNumber;
       VeniceSystemStoreType type = VeniceSystemStoreType.getSystemStoreType(store.getName());
       if (type != null && store.isSystemStore()) {
+        // metaStoreName is user system store
         largestUsedRTVersionNumber = ((SystemStore) store).getVeniceStore().getLargestUsedRTVersionNumber();
       } else {
+        // metaStoreName is zkShared system store
         largestUsedRTVersionNumber = store.getLargestUsedRTVersionNumber();
       }
       String rt = Utils.getRealTimeTopicName(store, largestUsedRTVersionNumber);