private boolean isExpired(long expirationTimeInMs, long referenceTimeInMs) {
    return expirationTimeInMs != Utils.Infinite_Time && expirationTimeInMs < referenceTimeInMs;
  }
Determine whether a blob is expired or not given the expiration time and a reference time.
@param expirationTimeInMs the expiration time of the blob in ms
@param referenceTimeInMs the reference time in ms until which expiration are relevant
@return whether the blob is expired or not
ambry-store/src/main/java/com/github/ambry/store/BlobStoreStats.java