Rate limits and temporary outages

Networking Senior Swift 5.5+ iOS 16+ Reviewed 31 Oct 2026 By Alok Singh

Pick the fix

The server returns 429 with Retry-After: 30. What should the client do?

OptionsPause matching requests for 30 seconds through a shared limiter, show cached data, then retryRetry immediatelyRetry each request with its own 1-second backoffLog the user out

Hint 1 of 1

What does Retry-After tell you?

Choose an answer, then open Show answer below to check it.

Show answer

Answer: A Pause matching requests for 30 seconds through a shared limiter, show cached data, then retry

Correct. It respects the server and keeps the UI useful.

Why not the others?

B Retry immediately. It makes the overload worse.
C Retry each request with its own 1-second backoff. Uncoordinated retries ignore the server's instruction.
D Log the user out. 429 means slow down, not an auth failure.

30-second answer

Treat 429 and 503 as signals: honour Retry-After, back off with jitter, and share one limiter across the app so every caller slows down together. Add a circuit breaker that stops calls for a while after repeated failures, coalesce duplicate requests, and show cached data with a clear offline or retry state instead of spinning forever.

Practise saying it · 45 s. No recording, just a timer

Explain how you handle rate limits.

Say your answer out loud, then check which of these points you covered:

Honour Retry-After
Shared limiter
Circuit breaker
Cached fallback

Deep dive

Coalesce identical in-flight requests so a screen doesn't fire the same call twice.

Prioritise user-visible requests over prefetches.

Log failure rates so you see outages before users report them.

Back off background refresh more aggressively than foreground.

Common mistakes

Each request retrying independently.
Ignoring Retry-After.

Senior take & follow-ups

Seniors design the client to cooperate with the server under stress.

Follow-up questions

Think of your answer first, then open the hint.

What is a circuit breaker?
Show hint
After N failures, fail fast for a cool-down period, then try one request.
Where does the limiter live?
Show hint
In the shared client, often an actor.

Suggest a fix if something here is wrong or out of date.