@Override public boolean doesPartitionExist(String catName, String dbName, String tblName, List<FieldSchema> partKeys,
      List<String> partVals) throws MetaException, NoSuchObjectException {
    catName = normalizeIdentifier(catName);
    dbName = StringUtils.normalizeIdentifier(dbName);
    tblName = StringUtils.normalizeIdentifier(tblName);
    if (!shouldCacheTable(catName, dbName, tblName) || (canUseEvents && rawStore.isActiveTransaction())) {
      return rawStore.doesPartitionExist(catName, dbName, tblName, partKeys, partVals);
    }
    Table tbl = sharedCache.getTableFromCache(catName, dbName, tblName);
    if (tbl == null) {
      // The table containing the partition is not yet loaded in cache
      return rawStore.doesPartitionExist(catName, dbName, tblName, partKeys, partVals);
    }
    return sharedCache.existPartitionFromCache(catName, dbName, tblName, partVals);
  }
This starts a background thread, which initially populates the SharedCache and later
periodically gets updates from the metastore db

@param conf
@param runOnlyOnce
@param shouldRunPrewarm
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/cache/CachedStore.java