Caching
Temporarily storing frequently-used data somewhere fast to access, so the system doesn't have to recompute or refetch it every time.
Think of it like
Like keeping a pitcher of pre-made lemonade in the fridge instead of squeezing fresh lemons for every single glass.
Junior or senior?
Junior sounds like
Describes caching only as making things faster.
Senior sounds like
Can discuss cache invalidation — a real time cached data went stale and caused a bug, and how they fixed it.
Ask them
“Tell me about a time cached data went stale and caused a bug. How did you fix it?”
Sounds like real experience
Names a specific stale-cache bug — what broke, how they noticed it, and the specific invalidation strategy (TTL, event-based) they put in place.
Probe further if
Describes caching only as 'making things faster' and credits the cache itself for the speedup, without describing a bug or invalidation decision they personally had to make.