Backpressure

You might say

When downstream processing cannot keep up, do not let the queue and memory grow forever. Slow or pause the upstream and resume after recovery.

Backpressure sends a downstream slowdown or pause signal upstream to limit new or unfinished workIf an image-processing service can finish only a small number of tasks per second while uploads keep arriving, queue length and memory grow without backpressure. The system can slow or pause publishing, or cap unacknowledged work, then resume when capacity recovers. Backpressure is not extra capacity and is not a fixed rate limit independent of downstream state.
Further reading