public boolean isBlobExist(String bucket, String uid) throws Exception {
        /**
         * b2_download_file_by_name $0.004 per 10,000 cheaper 10x times
         * b2_list_file_names $0.004 per 1,000
         */
        try {
            B2DownloadByNameRequest downloadRequest = B2DownloadByNameRequest.builder(bucket, uid)
                    .setRange(B2ByteRange.between(0, 1)).build();

            EmptyBlobSink sink = new EmptyBlobSink();
            client.downloadByName(downloadRequest, sink);
            long length = sink.getResponseHeaders().getContentLength();

            return length > 0;

        } catch (B2Exception e) {
            if (e.getStatus() == 404 && e.getMessage().contains("does not have file"))
                return false;
            else throw e;
        }
    }