HttpClient 429 spikes after deploy in .NET
Deploy finishes, traffic looks normal, then 429 errors spike and retries make it worse. This usually means Retry-After is ignored, concurrency ramps too fast, or retry budgets are too loose.
Common symptom variants
Primary playbook
When retries multiply 429 errors instead of fixing them: how retry amplification happens, how to prove it, and how to honor Retry-After with budgets.
Recommended resource
A copy/paste handler that parses Retry-After (seconds and HTTP date) plus a 429 runbook and logging fields so throttling becomes bounded, observable, and non-amplifying in .NET.
Related posts
Polly retries making outages worse: stop retry storms with backoff and jitter
When retries amplify failures instead of fixing them: how retry storms happen in .NET, how to prove it, and the four components that stop cascading failures.
Retries making outages worse: when resilience policies multiply failures in .NET
Retry storms don't look like a bug—they look like good engineering until retries amplify failures and multiply in-flight requests during backpressure.