@Override
  public CompletableFuture<Void> updateAsync(K key, U update) {
    throw new SamzaException("Caching not supported with updates");
  }
Lookup the cache and return the keys that are missed in cache
@param keys keys to be looked up
@param records result map
@return list of keys missed in the cache
samza-core/src/main/java/org/apache/samza/table/caching/CachingTable.java