private Long getCurrentKey() {
    long currentKey;
    if (lastPeekedId.get() == -1) {
      currentKey = getHeadKey();
    } else {
      currentKey = inc(lastPeekedId.get());
    }
    return currentKey;
  }
Finds the next object after the last key peeked
geode-core/src/main/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderQueue.java