I read these messages into a concurrent queue, and another thread (this is handled by the connect framework) will poll this queue and release the memory.

sleep

can avoid putting too many messages in the queue.

Send the messages via a coroutine channel. Instead of concurrent queues. The channel can be limited in size and will suspend your coroutine until more space becomes available. No blocking, no sleep, no delay: https://github.com/Kotlin/kotlinx.coroutines/blob/master/coroutines-guide.md#channels