HTTP 429 Too Many Requests vs 503 Service Unavailable
HTTP 429 (Too Many Requests) is a 4xx Client Error response, while 503 (Service Unavailable) is a 5xx Server Error response. 429 indicates that the user has sent too many requests in a given time (rate limiting). The response should include a Retry-After header. In contrast, 503 means that the server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
Description
The user has sent too many requests in a given time (rate limiting). The response should include a Retry-After header.
When You See It
When hitting API rate limits or making too many requests too quickly.
How to Fix
Check the Retry-After header. Implement exponential backoff. Consider caching responses.
Description
The server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
When You See It
During maintenance windows, server overload, or when the application pool is exhausted.
How to Fix
Wait and retry. Check the Retry-After header. Scale up servers if it's a capacity issue.
Key Differences
429 is a 4xx Client Error response, while 503 is a 5xx Server Error response.
HTTP 429: The user has sent too many requests in a given time (rate limiting). The response should include a Retry-After header.
HTTP 503: The server is temporarily unable to handle the request due to maintenance or overload. Should include a Retry-After header.
You encounter 429 when when hitting API rate limits or making too many requests too quickly.
You encounter 503 when during maintenance windows, server overload, or when the application pool is exhausted.
When to Use Which
For 429 (Too Many Requests): Check the Retry-After header. Implement exponential backoff. Consider caching responses. For 503 (Service Unavailable): Wait and retry. Check the Retry-After header. Scale up servers if it's a capacity issue.