The Postgres log by itself does not look like the fatal error.

The key lines are:

database system was not properly shut down; automatic recovery in progress
invalid record length ... redo is not required
checkpoint complete

That is a normal crash-recovery path after an unclean shutdown. invalid record length ... redo is not required is usually the end of WAL, not the cause of the 503. If Postgres logs later show database system is ready to accept connections, the database recovered and the next place to debug is the n8n service.

I would check it in this order:

1. Open the n8n service logs at the same timestamp and find the first fatal line after Postgres finishes recovery. The useful error will usually be in the n8n logs, not the Postgres logs. Look for:

database is not ready
ECONNREFUSED
ENOTFOUND
password authentication failed
relation ... does not exist
encryption key mismatch
server is listening on localhost

1. Confirm the n8n service is using Postgres variables from the current Postgres service, not stale copied values from an old database:

DB_TYPE=postgresdb
DB_POSTGRESDB_HOST=${{Postgres.PGHOST}}
DB_POSTGRESDB_PORT=${{Postgres.PGPORT}}
DB_POSTGRESDB_DATABASE=${{Postgres.PGDATABASE}}
DB_POSTGRESDB_USER=${{Postgres.PGUSER}}
DB_POSTGRESDB_PASSWORD=${{Postgres.PGPASSWORD}}

If you recreated or restored the Postgres service, do not trust manually copied host/user/password values. Replace them with Railway reference variables so they track the actual service.

1. Make sure n8n is binding to Railway's injected port:

N8N_PORT=${{PORT}}
N8N_LISTEN_ADDRESS=0.0.0.0

A Railway 503 normally means the edge could not reach a healthy HTTP process for the service. If n8n is stuck during DB startup, crashing on a migration, or listening on the wrong interface/port, the browser symptom can still be a 503 even though Postgres recovered.

1. Keep the existing N8N_ENCRYPTION_KEY unchanged. If that key changed while the database volume stayed the same, n8n can start but fail when loading saved credentials and workflows.

2. Restart in this sequence:

Postgres service -> wait for "ready to accept connections"
n8n service -> watch deploy logs until the editor starts
workers/webhook services, if your template uses them

If it still fails after that, paste the first n8n error after the Postgres recovery block. The snippet above is enough to show Postgres recovered, but it is not enough to identify why n8n is returning 503.