@Override
  public void writeExternal(ObjectOutput out) throws IOException {
    DataSerializer.writeByteArray(membershipID, out);
    DataSerializer.writeByteArray(getOptimizedByteArrayForEventID(threadID, sequenceID),
        out);
    out.writeInt(bucketID);
  }
Returns a byte[] whose contents are calculated by calling
{@link #getOptimizedByteArrayForEventID}

@since GemFire 5.7
geode-core/src/main/java/org/apache/geode/internal/cache/EventID.java