private boolean overwritingOldTombstone(InternalRegion region, VersionStamp stamp, VersionTag tag,
      StringBuilder verbose) {
    // Tombstone GC does not use locking to stop operations when old tombstones
    // are being removed. Because of this we might get an operation that was applied
    // in another VM that has just reaped a tombstone and is now using a reset
    // entry version number. Because of this we check the timestamp on the current
    // local entry and see if it is old enough to have expired. If this is the case
    // we accept the change and allow the tag to be recorded
    long stampTime = stamp.getVersionTimeStamp();
    if (isExpiredTombstone(region, stampTime, isTombstone())) {
      // no local change since the tombstone would have timed out - accept the change
      if (verbose != null) {
        verbose.append(" - accepting because local timestamp is old");
      }
      return true;
    } else {
      return false;
    }
  }
perform conflict checking for a stamp/tag
geode-core/src/main/java/org/apache/geode/internal/cache/entries/AbstractRegionEntry.java