I'm experiencing a persistent Redis connection issue in my NestJS application. The app starts successfully but immediately fails to connect to Redis with ECONNREFUSED errors, causing healthcheck failures.

Environment Details:

Project: lumen

Environment: Development

Region: EU West (europe-west4-drams3a)

Development Service ID: c94d8ea5-f995-4c07-9465-365371abde40

Redis Service ID: b35df8da-a1af-4e49-86db-313f9588b2b8

Latest Deployment ID: a4987cb5-241b-4d99-a2bb-c36afbab941c

Current Configuration:

REDIS_URL=redis://default:${{Redis.REDIS_PASSWORD}}@${{Redis.RAILWAY_PRIVATE_DOMAIN}}:6379

Problem:

NestJS app starts successfully and binds to port 8080

Immediately after startup, ioredis throws continuous AggregateError [ECONNREFUSED] errors

Redis service is healthy and running (1/1 replicas, no failures)

Error is ECONNREFUSED (TCP connection refused), not ENOTFOUND (DNS failure)

Healthcheck fails with: MaxRetriesPerRequestError: Reached the max retries per request limit (which is 20)

Critical observation: Logs show "[RedisService] Redis connected" immediately followed by ECONNREFUSED errors, suggesting a race condition

Attempted Fixes (all failed):

Corrected service name from redis-dev to Redis

Tried using ${{ Redis.REDIS_URL }}

Tried using ${{ Redis.REDIS_PUBLIC_URL }}

Tried hardcoded private domain with reference variables for password

Disabled healthcheck - connection still fails

Multiple redeployments