Hey thatnks for all the advice, I greatly appreciate it, but I used the agent to help implement some if not all of these changes and yet the same issue still applies. Is there potentially anything else I could be missing or should I go more into detail regarding these points?

Nevermind it works now! There were a couple things we had to add but it works! Thanks so much for the advice I appreciate it so much. Here's the last thing my agent did for me:

it appears there's the same issue or atleast something similar. The time for this error to pop up is as fast as before -- basically instantly:

Access to XMLHttpRequest at 'https://ai-interview-simulator-production-3d2c.up.railway.app/api/v1/auth/register' from origin 'https://ai-interview-simulator-nu-five.vercel.app' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. ai-interview-simulator-production-3d2c.up.railway.app/api/v1/auth/register:1 Failed to load resource: net::ERR_FAILED

The error is appearing instantly, which means the request isn't even reaching your backend. It's failing at the preflight OPTIONS request stage. Let me check if the app is actually running and responding:

Searched deploy logs

Hide result

19:57:47

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

19:57:47

await app(scope, receive, sender)

19:57:47

File "/usr/local/lib/python3.12/site-packages/slowapi/middleware.py", line 128, in dispatch

19:57:47

File "/usr/local/lib/python3.12/site-packages/starlette/routing.py", line 715, in call

19:57:47

return await call_next(request)

19:57:47

await self.middleware_stack(scope, receive, send)

19:57:47

^^^^^^^^^^^^^^^^^^^^^^^^

19:57:47

File "/usr/local/lib/python3.12/site-packages/starlette/routing.py", line 735, in app

19:57:47

File "/usr/local/lib/python3.12/site-packages/starlette/middleware/base.py", line 163, in call_next

19:57:47

await route.handle(scope, receive, send)

...and 40 more logs

Searched HTTP logs

OK! Now I can see the real issue. The HTTP logs show:

OPTIONS request: 200 OK (CORS preflight succeeded!)

POST request: 500 Internal Server Error

So CORS is actually working now — the preflight passed. The problem is your backend is crashing with a 500 error. Looking at the deploy logs, I see a massive stack trace from Redis:

File "/usr/local/lib/python3.12/site-packages/limits/storage/redis.py", line 224, in incr

Your rate limiter (slowapi) is trying to hit Redis to record the request, but it's crashing. And then:

Railway rate limit of 500 logs/sec reached for replica, update your application to reduce the logging rate.

The application is logging errors so fast it's hitting Railway's own log rate limit. Let me update my memory and then fix this:

The issue is the rate limiter. Let me check your main.py to see how it's configured:

Read file: backend/app/main.py

The rate limiter is being added. Let me check how it's configured in app/core/rate_limit.py:

Searched repository: **/rate_limit.py

Read file: backend/app/core/rate_limit.py

The rate limiter is configured to use Redis. The problem is it's crashing when trying to connect to Redis. Let me check the config to see if RATE_LIMIT_ENABLED can be disabled:

The issue is that the rate limiter is trying to use Redis but there's likely a connection issue. The simplest fix: disable the rate limiter since it's causing crashes:

Staged service update

Update "ai-interview-simulator"

Deployed

Deployed service

ai-interview-simulator

accf7f03

Removed

Done. Deploying with rate limiting disabled. Give it 30 seconds, then try your registration again. The 500 errors should be gone and your CORS requests should work.

I have seen threads with similar issue, if you want to put two commands in the start command, you need to wrap it in a shell like this

sh -c "alembic upgrade head && uvicorn app.main:app --host 0.0.0.0 --port 8000 --workers 1"