@Override
  public void addDestroyedEntry(Object key) {
    // assert if ri then readLock held
    // assert if gii then lock held
    if (isReplicate() || isClient()) {
      destroyedEntryKeys.put(key, Boolean.TRUE);
    }
  }
Using CM as a Set of keys
geode-core/src/main/java/org/apache/geode/internal/cache/UnsharedImageState.java