Diagnosis: Sudden slowdown = one of four culprits: memory/CPU spike, database query bottleneck, missing index, or Railway sleeping your service.

Step 1 — Check Railway metrics immediately: Dashboard → your service → Metrics tab → look for CPU/RAM spike at the exact time it slowed.

Step 2 — Check if service is being throttled:

railway logs --tail 100

Look for: OOM, killed, memory limit, timeout, rate limit

Step 3 — If database is the culprit (most common), run:

-- Find slow queries (PostgreSQL)
SELECT query, mean_exec_time, calls
FROM pg_stat_statements
ORDER BY mean_exec_time DESC
LIMIT 10;

-- Check for missing indexes
SELECT schemaname, tablename, attname, n_distinct, correlation
FROM pg_stats
WHERE tablename = 'your_table_name';

Step 4 — Add indexes on frequently queried columns:

CREATE INDEX CONCURRENTLY idx_table_column ON your_table(column_name);

Step 5 — If Node.js/Java service, check for memory leak: Add to Railway environment variables:

NODE_OPTIONS=--max-old-space-size=512

Step 6 — Force restart the service:

railway redeploy

Step 7 — Scale up temporarily while debugging: Dashboard → Service → Settings → Resources → bump RAM to next tier.

Step 8 — Enable Railway's health check to auto-restart on hang: In railway.toml:

[deploy]
healthcheckPath = "/health"
healthcheckTimeout = 30
restartPolicyType = "on_failure"
restartPolicyMaxRetries = 3

Most likely fix order:

1. Check metrics → identify spike time
2. Restart service immediately
3. Run slow query check on DB
4. Add missing indexes
5. Redeploy with health check config