Your question is Optimizing QVC Order Summary Queries. 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).
You are asked to explain how you would optimize a slow PostgreSQL query that builds a monthly customer summary from QVC order, customer, and item-level tables. Focus on how you would diagnose the issue, rewrite the SQL, and preserve correctness.
A common pattern is a query that joins qvc_orders, qvc_order_items, and qvc_customers, groups results by customer and month, and runs slowly because too many rows are scanned or joined before filtering.