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API Rate Limit 429 Too Many Requests — Handling Rate Limiting Headers

Warning4xx client error

Overview

Fix HTTP 429 Too Many Requests errors by implementing proper rate limit handling, reading rate limit headers, and using backoff strategies.

Key Details

  • HTTP 429 indicates the client has sent too many requests in a given time window
  • Rate limit headers (X-RateLimit-Limit, X-RateLimit-Remaining, Retry-After) indicate quota status
  • The Retry-After header specifies how many seconds to wait before sending another request
  • Rate limits are typically per API key, per IP, or per user depending on the API provider
  • Aggressive retry without respecting rate limits can result in temporary or permanent API bans

Common Causes

  • Application sending requests faster than the API's rate limit allows
  • Multiple application instances sharing the same API key and collectively exceeding limits
  • Retry logic without backoff creating a thundering herd effect
  • Batch processing or data migration scripts not implementing request throttling

Steps

  1. 1Read rate limit response headers to understand your current quota: X-RateLimit-Remaining and X-RateLimit-Reset
  2. 2Implement exponential backoff with jitter when receiving 429 responses
  3. 3Honor the Retry-After header value — wait at least that many seconds before retrying
  4. 4Use request queuing or token bucket algorithm to spread requests evenly across the rate window
  5. 5Consider upgrading your API plan or requesting a rate limit increase for legitimate high-volume use cases

Tags

rate-limit429throttlingapiretry-after

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Frequently Asked Questions

Wait 1s, then 2s, then 4s, then 8s, etc. (exponential) plus a random delay (jitter) to prevent multiple clients from retrying at the exact same time, which would cause another rate limit spike.