7 questions to ask before adding a cache: framework treats caching as a design decision, not a default

blaizedsouza · x · 2026-09-19

Raul Junco of System Design Classroom argues most caching bugs come from bad judgment — caching the wrong thing, too early, or without a reason — not from Redis or Memcached. He proposes a 7-question framework to turn caching into a deliberate design decision, starting with: is the data accessed frequently? Low-traffic data just wastes space; high hit rates across users are where caching saves real work.

Uncritical caching leads to stale prices for users, debugging coin-tosses between DB and cache, tripled memory footprint with eviction eating the wrong keys, and orphaned keys no one remembers.

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