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Cache Problems — Overview#

Four failure modes that all look the same on the outside — the DB gets hammered — but have completely different causes and require different fixes. Diagnosing which one you have determines which solution to reach for.

Files in this folder#

File Topic
01-Cache-Stampede.md One hot key expires — thousands of requests hit DB simultaneously
02-Cold-Start.md Cache is empty — every request misses, DB sees full traffic
03-Cache-Penetration.md Keys that don't exist bypass cache forever
04-Cache-Avalanche.md Thousands of keys expire at the same time
05-Interview-Cheatsheet.md Diagnose fast, fix correctly

The diagnostic question#

DB is being hammered. Which problem is it?

Is the cache empty?                           → Cold Start
Does one specific popular key keep expiring?  → Cache Stampede
Are requests for non-existent keys flooding?  → Cache Penetration
Did many keys expire at the same time?        → Cache Avalanche