Caching

Cache Avalanche

Many keys expiring at the same moment because they were populated together with identical TTLs.

Why interviewers ask about it

Fixed with one line: add random jitter to every TTL. Frequently the cheapest reliability improvement available.

A hot key expires and thousands of concurrent requests all miss and hit the origin simultaneously.

This term is part of the free System Design interview preparation module - browse the full glossary for every definition.