Backpressure reaches the producer

Asynchronous sends can outrun the receiver. Bound fan-out against scarce resources and make the producer participate in the flow-control policy.

Book basis: B333, B433.

Failure it prevents

A bounded consumer hides an ever-growing upstream mailbox or set of waiting producers.

Our Effect 4.0.0 reading

Queue.bounded suspends offers at capacity. Queue.dropping and Queue.sliding choose loss policies. Bounded Effect.forEach and Semaphore cap active work. Upstream backlog needs its own bound.

Source: packages/effect/src/Queue.ts, packages/effect/src/Effect.ts, packages/effect/src/Semaphore.ts.

How to check

Run a faster producer against a slower consumer. Check backlog and memory, plus the documented wait, reject, or drop behavior. This check is our proposal. The books do not prescribe it.

Continue with Admission control protects recovery10, Bulkheads isolate scarce capacity10.

Connect this to the existing rat-stack guidance23.

Use the durability skill for the full review. Return to the durability index34.

Sources

  1. Gray II, James Edward; Tate, Bruce A. Designing Elixir Systems with OTP. Pragmatic Bookshelf, 2019.. Pragmatic Bookshelf. Build a Functional Core; Isolate Process Machinery in a Boundary; Customize Your Lifecycle; Big, Loud Worker-Bees; Add Persistence as a Boundary Service; Test the Boundary. Accessed 2026-10-23.
  2. Nygard, Michael T. Release It!: Design and Deploy Production-Ready Software. Pragmatic Bookshelf, 2007.. Pragmatic Bookshelf. §4.4 Unbounded Result Sets; Chapter 5 Stability Patterns: §5.1 Timeouts, §5.2 Circuit Breaker, §5.3 Bulkheads, §5.4 Steady State, §5.5 Fail Fast, §5.6 Handshaking, §5.7 Test Harness, §5.8 Decoupling Middleware. Accessed 2026-10-23.
  3. Effect contributors. Effect 4.0.0. Queue.ts. Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.
  4. Effect contributors. Effect 4.0.0. Effect.ts. Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.
  5. Effect contributors. Effect 4.0.0. Semaphore.ts. Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.

Last changed 2026-10-23 in 58dc623. Source on GitHub. Change log.

Linked from

  1. Admission control protects recovery. Refuse or defer work that cannot be served usefully under current load.

    Continue with Retry load needs a budget, Backpressure reaches the producer.¶

  2. Agent guide. An Effect stack so pure (aspirational) Kit Langton will blush.

    Backpressure reaches the producer — Bounded consumption helps only when upstream respects waiting or refusal.

  3. Bulkheads isolate scarce capacity. Reserve independent capacity for workloads that must not starve each other.

    Continue with Backpressure reaches the producer, Effect is not BEAM.¶

  4. Change log. What changed in the files served here, newest first.

    Backpressure reaches the producer — new page: docs(lore): land the durability wiki pages and bibliography

  5. Concurrent work needs an owner and a bound. Limit active work, retain result order, and stop child work when its owning lifetime ends.

    Backpressure lets the consumer limit how quickly the producer can continue.

  6. durability. Keep a rat-stack app standing when a provider, pool, or dependency slows down or a worker dies. Use at any I/O boundary, connection pool, provider call, shared waiter, fan-out, flag, gate, or work that can outlive a request, or when asked "what happens when this is slow", "add a timeout", "make this durable", or "what survives a crash".

    Backpressure reaches the producer and bulkheads isolate capacity.¶

  7. Durability starts with a recovery record. A reading order for storage, replay, worker ownership, overload, and recovery tests.

    Backpressure reaches the producer: Bounded consumption helps only when upstream respects waiting or refusal.¶

  8. Full agent guide. An Effect stack so pure (aspirational) Kit Langton will blush.
  9. Rat Stack lore | rat-stack. Short, source-grounded notes on the ideas and decisions behind rat-stack.

    Backpressure reaches the producer — Bounded consumption helps only when upstream respects waiting or refusal.

  10. Source change history (log.md). The generated change log as Markdown.

    Backpressure reaches the producer — new page: docs(lore): land the durability wiki pages and bibliography