API Gateway dropping valid JWT requests unexpectedly

Yuso Faisyahhhhh 80 Reputation points
2026-09-16T09:28:29.3833333+00:00

I'm facing an issue where the API Gateway sometimes drops legitimate requests even though the JWT authentication is valid. The traffic volume is pretty low, so I’m not sure why the rate limiting would be triggered in the first place. I want to like to check whether the rate limit key rules are grouping requests incorrectly or counting them unexpectedly. Is there a way to audit the rate limit configuration and see exactly which key or rule is causing these requests to be dropped ?

Windows for business | Windows 365 Enterprise
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HLBui 12,460 Reputation points Independent Advisor
2026-09-16T10:30:10.1466667+00:00

Hi Yuso Faisyahhhhh

I think your API Gateway is being a bit over‑protective here valid JWTs getting dropped usually means the rate‑limit evaluator is grouping requests under the wrong key, so even low traffic can accidentally trip a threshold. A good first step is to turn on rate‑limit key debugging so you can see exactly which key (IP, user ID, client ID, custom header, etc.) is being counted. Most gateways also let you enable verbose policy tracing, which will show you the rule evaluation path and why a request was rejected.

From there, please checking whether any of your key selectors are too broad , for example, a shared NAT IP or a mis‑parsed header can cause multiple users to collapse into one rate‑limit bucket. You can also use rate‑limit audit commands to dump the active counters and confirm which rule is firing. Once you identify the culprit, adjusting the selector or splitting the key space usually stabilizes things right away.

If this helps you narrow down the issue, kindly hit Accept Answer so others running into the same API Gateway behavior can find the solution more easily.

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  1. AI answer

    2026-09-16T09:28:46.38+00:00

    Yes. In Azure API Management, the supported way to audit why requests are being throttled is to inspect the effective policy and the API Management inspector trace.

    1. Check the inspector trace for the affected request.
      • Review the inbound processing trace and look for rate-limit or rate-limit-by-key policies.
      • This shows whether throttling is coming from a policy at Global, Product, API, or Operation scope.
    2. Use Calculate effective policy.
      • This shows the final policy after inheritance is applied.
      • It helps confirm whether a throttling policy is active at the scope handling the request.
    3. Verify the counter-key used by rate-limit-by-key.
      • API Management uses a single counter for each counter-key value.
      • If the same key value is used at multiple scopes, the counter is updated at all those scopes.
      • If separate counters are needed, different key values must be used for different scopes.
    4. Check whether the policy uses increment-condition or increment-count expressions.
      • When either is defined with expressions, evaluation and increment are postponed until the end of the outbound pipeline.
      • In that case, the 429 Too Many Requests condition can be evaluated on the next incoming call, which can make the throttling appear unexpected.
    5. If the throttling policy is configured at Product scope, verify that subscription context is resolved for the request.
      • Product-scope policies are applied only when API Management can resolve a subscription context.
      • If no subscription key or alternative subscription resolution mechanism is used, product policies are skipped.
    6. Keep in mind that rate limiting is not perfectly exact.
      • Because throttling is distributed, the configured limit and actual enforcement can vary depending on request volume, backend latency, and related factors.

    If the goal is to identify exactly which rule is causing the drop, the most direct path is:

    • capture a failing request,
    • open the API Management inspector trace,
    • confirm the throttling policy shown in inbound processing,
    • then use Calculate effective policy to identify the scope and inspect the counter-key, increment-condition, and inherited policy behavior.
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