Long getCrcOfKey(StoreKey key) {
    return recentCrcs.get(key);
  }
Returns the crc associated with this key in the journal if there is one; else returns null.
@param key the key for which the crc is to be obtained.
@return the crc associated with this key in the journal if there is one; else returns null.
ambry-store/src/main/java/com/github/ambry/store/Journal.java