Why API Retry Logic Needs Exponential Backoff and Jitter to Avoid Outages

Poorly designed API retry mechanisms can turn brief server outages into prolonged failures, as simultaneous retries from thousands of clients can quadruple server load in seconds. This phenomenon, known as a retry storm or thundering herd, is well documented in Google's SRE literature as a cause of cascading failures. A reliable retry strategy must distinguish between retryable errors — such as 429, 502, 503, and 504 status codes — and non-retryable client-side errors like 400, 401, and 403. Exponential backoff with full jitter, which randomizes wait times between zero and a capped maximum, prevents clients from synchronizing retries and reduces request spikes. Additional safeguards such as idempotency keys, Retry-After header compliance, retry budgets, and circuit breakers are recommended for production-grade implementations.