• max_message_size is the maximum message size a reader/writer will accept to receive/send.

• max_buffer_size is the maximum size the internal reader/writer's buffer will ever grow.

• write_timeout is the maximum time allowed for a write operation to complete before an error is reported.

• When the writer's internal buffer is filled at buffering_threshold_in_bytes or more, the writer will try to flush its buffer immediately. This is to get good latency and avoid buffering too much when sending big batches of messages.

• If the application hasn't sent any messages in the current Async job and nothing is buffered, the first start_batching_after_num_messages messages will be sent immediately. After that the writer will start buffering. This is to give good latency when the application sends a few messages occasionally but still get good throughput when sending a batch of messages.

Note that start_batching_after_num_messages and buffering_threshold_in_bytes have somewhat opposite meanings: the former determines when to start batching and the latter determines when to write data that has been batched.