Back-Pressure (Async Programming Context)¶
The general back-pressure concept is covered in full depth in Back-Pressure. This page focuses specifically on how it manifests within a single async runtime — bounded async channels/queues and async generators — rather than across network/service boundaries.
flowchart LR
Junior["Junior: why an unbounded async queue between producer and consumer tasks is dangerous"] --> Middle["Middle: bounded async channels as the fix"] --> Senior["Senior: backpressure through async generators specifically"]
Senior --> Professional["Professional: backpressure-aware async stream libraries at scale"]
flowchart LR
ProducerTask["Producer async task"] --> Channel["Bounded async channel\n(capacity N)"]
Channel --> ConsumerTask["Consumer async task"]
Channel -.full.-> ProducerWaits["Producer task SUSPENDS\n(not busy-waits) until\nspace frees up"]
Choose a level¶
| Level | Guide | You are done when |
|---|---|---|
| Junior | Unbounded async queues are still dangerous | You can explain why "it's async, so it's fine" doesn't protect against unbounded memory growth. |
| Middle | Bounded async channels | You can implement a producer/consumer pair using a bounded async queue that suspends (not blocks) when full. |
| Senior | Backpressure through async generators | You can explain how an async generator's consumer naturally provides backpressure by construction. |
| Professional | Backpressure-aware stream libraries | You can evaluate a reactive-streams-compliant async library's backpressure guarantees. |
Practice rule¶
An unbounded asyncio.Queue() (no maxsize) between a fast async producer and a slow async consumer has the exact same unbounded-memory- growth risk as any other unbounded queue covered elsewhere in this tree — "it's async" changes nothing about this risk.