# Three 5xx and one 4xx: the codes I actually care about

DevFeed: [Three 5xx and one 4xx: the codes I actually care about](<https://devfeed.tech/articles/three-5xx-and-one-4xx-the-codes-i-actually-care-about-34014.md>)

Original publisher: [Read original article](<https://sridharrajarao.com/blog/http-codes-at-scale/>)

Author: Sridhar Rajarao

Published: 2026-05-26T00:00:00Z

Content type: tutorial

Language: en

Sources: [Sridhar Rajarao](<https://devfeed.tech/sources/sridhar-rajarao.md>)

Topics: [HTTP](<https://devfeed.tech/topics/http.md>), [site-reliability-engineering](<https://devfeed.tech/topics/site-reliability-engineering.md>), [API](<https://devfeed.tech/topics/api.md>), [nginx](<https://devfeed.tech/topics/nginx.md>), [servers](<https://devfeed.tech/topics/servers.md>)

Tags: [api](<https://devfeed.tech/tags/api.md>), [http](<https://devfeed.tech/tags/http.md>), [load-balancer](<https://devfeed.tech/tags/load-balancer.md>), [nginx](<https://devfeed.tech/tags/nginx.md>), [production](<https://devfeed.tech/tags/production.md>), [reliability](<https://devfeed.tech/tags/reliability.md>), [scale](<https://devfeed.tech/tags/scale.md>), [sre](<https://devfeed.tech/tags/sre.md>)

## AI overview

An SRE-oriented guide to interpreting HTTP status codes 500, 502, 503, and 429 in production. It connects each code with likely causes and recommended operational responses, including checking logs, investigating backend failures, load shedding, and client backoff.

## Source excerpt

How I read 500, 502, 503, and 429 in production at scale, and what each one is really telling you.