Hi Railway team,

My deployed FastAPI backend is consistently showing:

"Application failed to respond"

HTTP 502 Bad Gateway (from Railway edge)

Healthcheck failures on /api/health

But internally, the application logs show:

Uvicorn starts successfully

"Application startup complete"

No crashes or stack traces

/api/health returns 200 OK when hit directly (sometimes via curl)

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# 📌 Environment Details

- Platform: Railway

- Region: asia-southeast1-eqsg3a

- Framework: FastAPI (uvicorn)

- Start command:

uvicorn app.main:app --host 0.0.0.0 --port $PORT --workers 1 --proxy-headers --forwarded-allow-ips "*"

- Healthcheck path: /api/health

- Deployment type: Nixpacks

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# 🚨 Problem Summary

1. Railway dashboard shows:

"Application failed to respond"

2. External requests sometimes fail with:

HTTP 502 Bad Gateway

{"message":"Application failed to respond"}

3. However:

- Container is running

- Uvicorn is bound to 0.0.0.0:$PORT correctly

- Startup logs show no crash

- Health endpoint works intermittently via curl

4. Example curl response:

- TLS OK

- Connection OK

- But Railway edge returns 502 intermittently

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# 🔍 What I already verified

PORT is correctly using Railway's $PORT (not hardcoded)

Only 1 worker (workers=1)

/api/health is lightweight and returns static JSON

No blocking code in startup

No DB dependency in healthcheck

MongoDB / Redis failures do NOT crash startup

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# ⚠ What seems broken

This appears to be a Railway edge routing / proxy issue, not an application crash.

Symptoms suggest:

- requests reach Railway edge

- but fail to properly route to running container OR timeout at edge layer

- intermittent 502 even when container is healthy

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# ❓ Request

Please help investigate:

1. Is there any known issue with:

- asia-southeast1-eqsg3a region routing

- edge proxy instability

- healthcheck misconfiguration

2. Can you confirm:

- whether traffic is reaching my container

- or failing at Railway edge before container

3. Any recommended fixes for:

- intermittent "Application failed to respond"

- 502 Bad Gateway despite healthy container

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# 📎 Additional info

- Same issue persists across redeploys

- Restart does not fix issue

- Curl sometimes works, sometimes returns 502

- No application-level errors seen in logs

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Thanks — this looks like a platform-level routing/healthcheck issue rather than application bug.