private static void handleSingleton(final @Nullable LocalRegion region,
      final @NotNull Object entryKey,
      final @NotNull InterestResultPolicy policy, final @NotNull ServerConnection servConn)
      throws IOException {
    final List<Object> keyList = new ArrayList<>(1);
    if (region instanceof PartitionedRegion) {
      keyList.add(entryKey);
      handleListPR((PartitionedRegion) region, keyList, policy, servConn);
      return;
    }
    if (region != null) {
      if (region.containsKey(entryKey)
          || sendTombstonesInRIResults(policy) && region.containsTombstone(entryKey)) {
        appendInterestResponseKey(region, entryKey, entryKey, keyList, servConn);
      }
    }
    // Send the last chunk (the only chunk for individual and list keys)
    // always send it back, even if the list is of zero size.
    sendRegisterInterestResponseChunk(region, entryKey, keyList, true, servConn);
  }
Process an interest request consisting of a single key

@param region the region
@param entryKey the key
@param policy the policy
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/BaseCommand.java