You are asked how to optimize a PostgreSQL query used in an Apptio cost reporting workflow when it becomes too slow as data grows. Explain how you would diagnose the bottleneck, what SQL anti-patterns you would check first, and how you would decide between rewriting the query, adding indexes, or changing the underlying data model.

Keep the answer practical. The interviewer is looking for a repeatable optimization process, not a generic list of tuning ideas. You should reference PostgreSQL-specific tools such as EXPLAIN ANALYZE and discuss how you would validate whether a change actually improves the query.