Act as a senior performance engineer. In my {{tech_stack}} app, {{page_or_feature}} feels slow. Don't optimize anything yet; first find out where the time goes. 1. Define the slowness. Is it slow to show anything, slow to fill in data, slow after a click or while typing, or slow only for some users, data sizes or times of day? Take one number for it now, measured the same way every time, on a throttled mid-range phone and on desktop. 2. Collect evidence: - Network tab: the waterfall for this page. Look for requests that wait on each other in a chain, very large responses, and the slowest time to first byte - Server or function logs and timings for those requests, including cold starts - Database: which queries this page runs, how many, and how long each takes; run explain on the slowest - Performance panel: long tasks, heavy rendering, and components re-rendering on every keystroke 3. Likely causes for one slow page: - Fetch waterfalls: data loaded one request after another that could load in parallel or in one query - N+1 queries: one query per item in a list - Missing indexes on columns used to filter, join or sort - Loading every row or column when the page shows 20 - Heavy work during render, or a big library loaded for one small feature - Huge images, or third-party scripts on this page 4. Confirm the top cause by measuring with and without it, then make the smallest fix and measure again the same way. Return the before and after numbers, the root cause in plain words, and a guard so it stays fixed, such as a query count check in a test or a time budget for this page. Don't add caching to hide a slow query without telling me what could go stale.