Retry Strategy Designer
Design optimal retry strategies with exponential backoff for API resilience
Retry Configuration
Retry Timeline
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What is a Retry Strategy?
A retry strategy defines how your application handles failed API requests by automatically attempting them again with calculated delays. Well-designed retry logic is essential for building resilient applications that gracefully handle transient failures, rate limits, and network issues.
This retry strategy designer helps you visualize and configure backoff algorithms. Input your parameters and see exactly when each retry will occur, helping you balance fast recovery against avoiding server overload.
Backoff Strategy Types
Exponential Backoff
Delay doubles (or increases by multiplier) with each retry. Most effective for rate limits—gives servers time to recover. Formula: delay = initial × multiplier^attempt
Linear Backoff
Delay increases by a fixed amount each retry. More predictable but less effective for congestion. Formula: delay = initial × attempt
Fixed Interval
Same delay between all retries. Simple but can cause thundering herd problems when many clients retry simultaneously.
Why Add Random Jitter?
When many clients hit a rate limit simultaneously, they all retry at the same calculated time—creating another spike that fails again. Adding random jitter spreads retries across time:
delay = baseDelay + random(0, baseDelay × jitterFactor)
AWS recommends "full jitter" where the actual delay is random between 0 and the calculated delay. This distributes load most effectively but may occasionally retry very quickly.
When Should You Retry?
| Error Type | Retry? | Notes |
|---|---|---|
| 429 Rate Limit | Yes | Use Retry-After header if provided |
| 500/502/503 Server Error | Yes | Transient; usually recovers quickly |
| Timeout | Yes | Network or server overload |
| 400 Bad Request | No | Client error; fix request first |
| 401/403 Auth Error | No | Credentials/permissions issue |
Retry Best Practices
- Set a maximum delay cap: Without a cap, exponential backoff can grow to hours. 60-120 seconds is typical.
- Limit total retries: 3-5 retries is usually sufficient. More wastes time if the issue persists.
- Log retry attempts: Track retry frequency to identify recurring issues and tune your strategy.
- Respect Retry-After headers: When APIs tell you when to retry, use that value instead of your calculated delay.
- Use idempotent operations: Ensure retrying doesn't cause duplicate side effects (double charges, duplicate records).
Frequently Asked Questions
What multiplier should I use for exponential backoff?
2x is the standard (binary exponential backoff). Use 1.5x for faster recovery or 3x when servers need more recovery time.
Should I retry on all errors?
No. Only retry transient errors (429, 5xx, timeouts). Retrying 4xx client errors wastes time—the request needs to be fixed first.
What's a good initial delay?
Start with 1 second (1000ms) for most APIs. For rate limits, 2-5 seconds may be more appropriate. Too short risks immediate re-failure.