DatabasesBackendHigh signal
Cache Invalidation
The problem of knowing when cached data has gone stale and needs to be refreshed or removed — famously one of the hardest problems in computer science because it's easy to get subtly wrong.
Think of it like
Like a restaurant's daily specials board that isn't updated after the kitchen runs out of the special, so customers keep ordering something that's no longer available.
Junior or senior?
Junior sounds like
Hasn't hit a real bug from stale cached data.
Senior sounds like
Has a real story about serving stale data and the invalidation strategy — TTL, event-based — they used to fix it.
Ask them
“Tell me about a bug caused by stale cached data. How did you decide when and how to invalidate it?”