Rate limiting

Rate limiting restricts how many requests a client may make within a time window. It protects infrastructure and is applied by nearly every substantial service.

#The 429 status code

429 Too Many Requests indicates you have exceeded a limit. A well-behaved server includes a Retry-After header saying when to try again — either in seconds or as a date.

HTTP/1.1 429 Too Many Requests
Retry-After: 30

#Reading it correctly

A 429 usually means your rate is wrong, not your proxy. Rotating to a new address and continuing at the same speed treats the symptom, consumes pool reputation, and often produces a harder block. Honour Retry-After when it is present.

#Backoff that works

Exponential backoff with jitter. Without jitter, parallel workers that fail together retry together and recreate the burst that caused the limit. Cap the maximum delay and cap the retry count — an uncapped retry loop is an outage generator.

#Reference

429 is specified in RFC 6585, section 4.