CAP Theorem
A principle stating a distributed database can't simultaneously guarantee Consistency (everyone sees the same data), Availability (every request gets a response), and Partition tolerance (it keeps working despite network failures) — it has to trade off between them.
Think of it like
Like a restaurant with one kitchen serving multiple dining rooms during a communication outage between them — it can keep every dining room serving customers (availability) or guarantee every order matches exactly (consistency), but not perfectly both during the outage.
Junior or senior?
Junior sounds like
Can recite the CAP theorem from memory.
Senior sounds like
Can name a real database choice their team made because consistency versus availability was the actual deciding factor.
Ask them
“Tell me about a database choice your team made where consistency versus availability was the actual deciding factor.”