private boolean isExpiredTombstone(InternalRegion region, long timestamp, boolean isTombstone) {
    return isTombstone
        && timestamp + TombstoneService.REPLICATE_TOMBSTONE_TIMEOUT <= region.cacheTimeMillis();
  }
perform conflict checking for a stamp/tag
geode-core/src/main/java/org/apache/geode/internal/cache/entries/AbstractRegionEntry.java