Tracks / SQL
SQL
Joins, indexes, isolation levels, and reading a query plan.
mid
Working knowledge. Where most loops are decided.
- Queries, joins & window functions10 questions
The SQL you will be asked to write on a whiteboard, with the reasoning behind each construct.
senior
Trade-offs and failure modes under follow-up pressure.
- Indexes, transactions & query plans10 questions
How indexes really work, isolation levels and their anomalies, locking, and reading EXPLAIN output.
- Query forensics Signal6 questions
Six database symptoms — a plan that flipped, an index that made things slower, a lock nobody can find, a migration that took the site down.
staff
Judgement, scope and the questions with no clean answer.
- What Postgres does with your query Deep10 sections
Parse, rewrite, plan, execute — plus buffers, WAL, MVCC, visibility and locks. The layer beneath every "add an index" answer.