Designing an Expiring Inbox System with Background Workers

Temporary email systems have one defining property: everything they create must eventually disappear. That sounds simple until you need to implement it in production. Expiring inboxes are not a UI gimmick — they are an operational requirement. Without reliable expiration, the database grows unboundedly. Anonymous inboxes pile up. Storage costs accumulate. More critically, without expiration enforcement at the ingestion layer, a mailbox that should have stopped receiving messages an hour ago might still accept them — silently, with no indication to the sender or recipient. This article documents the expiring inbox implementation in uncorreotemporal.com , a programmable temporary email infrastructure. The system is written in Python with FastAPI, PostgreSQL, Redis, and an async SMTP layer. We'll trace the full expiration path: from the database schema, through the background worker, through the delivery safeguard, and into the failure scenarios that shaped each design decision. The Probl