@Override
  protected void updateBlobTtl(String blobIdStr, final String serviceId, long expiresAtMs,
      FutureResult<Void> futureResult, Callback<Void> callback, QuotaChargeCallback quotaChargeCallback) {
    RouterException routerException =
        new RouterException("Illegal attempt to update TTL of blob through BackgroundDeleter",
            RouterErrorCode.UnexpectedInternalError);
    nonBlockingRouter.completeUpdateBlobTtlOperation(routerException, futureResult, callback);
  }
TTL update operations are disallowed in the BackgroundDeleter.
ambry-router/src/main/java/com/github/ambry/router/OperationController.java