Your question is Optimizing SQL Query Performance. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Query performance matters in production systems because slow SQL can increase latency, raise infrastructure costs, and block downstream workloads. Interviewers often ask this to assess whether you understand both query-writing habits and database behavior.
Explain how you optimize SQL queries for performance in PostgreSQL. Your answer should cover:
Keep the discussion at an easy, practical level. Focus on foundational techniques such as selecting only needed columns, filtering early, avoiding unnecessary work, using appropriate indexes, and validating changes with EXPLAIN or EXPLAIN ANALYZE. You do not need to cover advanced internals, but you should show a clear, structured approach to diagnosing and improving query speed.