static int estimateBatchSizeUpperBound(ByteBuffer key, ByteBuffer value, Header[] headers) {
        return RECORD_BATCH_OVERHEAD + DefaultRecord.recordSizeUpperBound(key, value, headers);
    }
Get an upper bound on the size of a batch with only a single record using a given key and value. This
is only an estimate because it does not take into account additional overhead from the compression
algorithm used.
clients/src/main/java/org/apache/kafka/common/record/DefaultRecordBatch.java