public Serde<WK> getKeySerde() {
    return keySerde;
  }
The following {@link Serde}s are serialized by the ExecutionPlanner when generating the store configs, and deserialized
once during startup in SamzaContainer. They don't need to be deserialized here on a per-task basis
samza-api/src/main/java/org/apache/samza/operators/windows/internal/WindowInternal.java