Queue Fan-Out Outperforms Monolithic Cron for Large Email Retry Workloads

The article argues that cron should only admit work, while a queue-backed worker sends each report email with bounded retries. Each job is keyed by report date and recipient or tenant ID, so redelivery under at-least-once semantics does not cause duplicate sends. Using a hypothetical 18,400-recipient digest that hits provider rate limits partway through, the author shows how a monolithic run forces risky restarts or manual cleanup. The approach lets operators retry only unfinished recipient jobs, and alerts can focus on exhausted attempts or message age rather than transient 429 responses. The piece also notes that payloads should stay small, since queue message bodies have size limits.