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Graph/azure-endpoint-mismatch

Pattern

Azure Routing/Response Mismatch

azure-endpoint-mismatch

A deployment-environment mismatch where FastAPI endpoints behave differently on Azure—returning 404s or missing SSE/CORS-delivered events—until server startup, routing/base paths, and platform limits (CPU/computation) are aligned.

Node Details

Public graph metadata

Updated4/30/2026

Connections

30 linked nodes

FastAPI route works locally on / but fails on Vercel

Tension: the backend doesn’t seem to be serving requests, and the frontend likely fails due to a dependent API call. Outcome: The deployment succeeds (`READY` state).

502 preflight error between Vue.js frontend and Express backend

When accessing a bad url supposed to be 404 have this error `This Serverless Function has crashed.` — Angular SSR deployed on Vercel Serveless Function. Tension: my angular app routing could never do the job of redirecting to the correct /404 or just display the 404 component.

Cannot find module '@azure/identity' — I deployed express app to Vercel. Tension: local and it works fine. Outcome: after deploy to vercel, I see this error.

Errors from an ASP.NET Core 7 app are not appearing in Sentry, and the console shows `CSRF Verification Failed A required security token was not found or was invalid`.

after some time I get a `503 Service Unavailable` error — When I make a POST request to this endpoint, it starts processing. Tension: especially when using ngrok. Outcome: What is the best way to handle long-running POST requests in FastAPI?

TypeError in FastAPI when using APIRoute with a Router — trying to implement an `APIRoute` class to handle logic before and after the request (logging). Outcome: Removing `async` before the function definition solved it.

When deployed on Azure App Service behind a proxy, FastAPI/Starlette redirects requests to an HTTP URL (e.g., HTTP Location header in a 307) instead of preserving HTTPS. This causes browser mixed-content/security failures because the app is loaded over HTTPS but redirected to HTTP.

it says `404 not found` — I succesfully deployed my FastAPI app to azure, but when I try to access the routes. Tension: However, when I tested the same routes locally, they worked. Outcome: I've successfully deployed your code to Azure Web App and have been able to access the routes.

the response headers from the FastAPI service don't have the `x-b3-spanid` and `x-b3-traceid` response headers — trying to get auto instrumentation working for a FastAPI service. Tension: but not having any luck.

Protect FastAPI routes so that authenticated users without the required permissions/roles cannot access specific endpoints.

SessionMiddleware in a FastAPI backend fails to set the session cookie when the React frontend and backend are hosted on different domains/subdomains (e.g., XXX-ui.fly.dev vs XXX-api.fly.dev). The browser rejects the cookie with an 'invalid domain' error and no session is maintained.

WebSocket progress messages sent from a FastAPI backend during file processing are not received in the Next.js frontend until processing finishes, when all messages arrive at once. Backend logs show progress updates are generated successfully.

When deployed behind a Kubernetes/API-gateway URL prefix (e.g., https://api-gateway.example.com/myapp), FastAPI tried to load OpenAPI from a path missing the prefix (e.g., /api/v1/openapi.json), causing a 404 and failing to load API definitions.

After moving SQL endpoints from `main.py` into an `APIRouter` in `analytics.py`, database dependencies that worked in `main.py` no longer function correctly and errors occur (e.g., import/circular dependency issues).

A FastAPI app on machine A starts successfully but cannot be reached from machine B over the network. Connections fail despite the server running without errors.

The Flutter Linux app calling local FastAPI endpoints fails with a DioException [bad response] due to an HTTP 307 (Temporary Redirect). Postman requests succeed, but the app always receives the redirect response.

Defining FastAPI routes in a loop causes each endpoint to behave like the last model

FastAPI returns 401 with JWK public Attribute for authorization token not found

Deployment fails silently when code includes azure-identity

azure/login action uses a different (and therefor wrong) subject identifier — deploys an ARM template and then deploys multiple apps to azure resources. Tension: results in the deployment of the apps failing.

Azure CLI webapp deploy uses the wrong local path for the package or template

New Azure project lacks a clear Bicep folder/template structure for multiple environments and resources

the workflow hangs on the "Post Run actions/checkout@v3" step until it eventually times out — deploying an Angular app to Azure Static Web Apps using GitHub Actions. Tension: the build process completes without errors, but the workflow hangs. Outcome: Azure couldn't do; hence it got hang & the process ran indefinitely.

A React frontend POST to http://localhost:4000/api/checkout consistently returns 404 Not Found even though an Express route for checkout is defined.

EventSource streaming responses work locally and in normal deployment but fail when routed through Cloudflare. The client does not receive a working text/event-stream stream.

The middleware fetches an Azure token using async logic, but RTK-Query proceeds without waiting, so requests are sent before the token is available. As a result, the token is not present at the correct time for data fetching.

GET /api/weather returns "unknown endpoint" from middleware instead of the expected JSON response

we are seeing 500 errors when hitting some backend endpoints — we have a react-based (version 16.14.0) PWA that is hosted on Microsoft Azure app service plans (premium tier). Tension: It is ONLY affects POST endpoints. GET endpoints successfully continue to work to these backends. Outcome: Current workaround is to change your app service to use http 1.1.

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