Quantify the Problem
Put numbers on the problem: how slow is it (8 seconds), how much data is involved (2M rows), what's the expected performance? Quantified problems lead to measurable fixes. 'The query is slow' is subjective: '8-second load time on 2M rows without an index' tells Claude exactly what to optimize.
Where you'll practice this
One Promptles scenario teaches this principle directly.
The Slow Query
Your admin dashboard takes 8 seconds to load. After profiling, you traced the bottleneck to the `getMonthlyReport()` function in `api/reports.ts`, which queries the `transactions` table. The table has 2 million rows and the query filters by `created_at` but there's no index on…