Quiz

2627 questions of the kind that actually get asked — in interviews, in architecture review boards, and by the person who has to run the thing at 3 AM. Every answer states the trade-off rather than the slogan, and says when the obvious choice is the wrong one.

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3 questions in Query Optimisation.

Quiz

A query that ran in 50ms for two years now takes 90 seconds. Nothing was deployed and the data volume grew normally. What happened?

An endpoint's p99 is 4 seconds. The database's slow query log is empty and CPU is low. What is happening?

In a multi-tenant platform where every tenant's data shares the same physical tables and tenants differ in size by orders of magnitude, why do query plans that are optimal for one tenant become pathological for another - and what is the fix?