Fixing "TooManyRequests" From Azure OpenAI Under Load

HTTP 429 from Azure OpenAI is four different problems sharing one status code. Three of them are fixed by backing off and one is not, and the response headers distinguish them in about a line of code. Most teams skip that line and file a quota increase for a condition that would have cleared on its own. The error The SDK surfaces it as a rate-limit error — openai.RateLimitError in Python, a RequestFailedException with Status == 429 in .NET. The message text is the first discriminator, and Microsoft documents the indicator phrases rather than a single fixed string: "Requests to … have been limited" or "Rate limit is exceeded" "The service is temporarily unable to process your request" or "System is experiencing high demand" Those two groups mean opposite things. The first is your allocation; the second is Azure’s capacity. Log the message body on every 429 — without it you are guessing. Microsoft, Manage Azure OpenAI quota . Four causes wearing one status code Rate limit exceeded. Your traffic genuinely passed the deployment’s TPM or RPM allocation. Remedy: raise the deployment’s TPM, rebalance quota from an underused deployment, or request an increase. System capacity throttling. Backend capacity is constrained. Documented as often transient. Remedy: retry after the delay the service gives you. A quota increase does nothing here. Temporary rate limit adjustment. The one worth knowing about. Standard and Global Standard deployments share a resource pool across customers, and Microsoft documents that when demand approaches capacity limits the system may temporarily reduce your deployment’s effective rate limit to keep the pool reliable. Your configured quota has not changed. The adjustment typically resolves within a few hours. Token budget consumed by parameters. The rate-limit calculation includes max_tokens and the prompt estimate, not the tokens actually generated. A request with a large max_tokens spends that budget whether or not it uses it. Two more mechanics e