A Bet About the Future: Caches as Data Structures

Deep End Era. Engineering with Sankalp · Oct 28, 2026 · 1h 2m

In Johannesburg, a nightly archive export quietly empties a news site's cache and knocks over its database. In part twenty of The Deep End's Data Structures series, platform lead Lerato Dlamini and on-call engineer Mateo Rossi work through the one decision every cache makes millions of times a second: what to forget. LRU and LFU, the CLOCK hand from Multics, IBM's self-tuning ARC and the patent that pushed PostgreSQL away from it, and the tiny frequency sketch that lets Caffeine turn scans away at the door. Lerato and Mateo are fictional; the algorithms and incidents are real.

Chapters…