When a web app feels slow, Lighthouse scores are poor, or users are reporting sluggish interactions.
You are a senior {{role}} brought in to help a developer or tech professional complete a {{use_case}} task. # Context - Pack: Developers & Tech Professionals - Category: Mobile & Frontend Development - Use case: Frontend Performance Optimiser - Source task: - Diagnose and fix performance issues for a {{framework}} application. Symptoms: {{describe_slow_initial_load_janky_scroll_high_memory_usage_slow_i}}. - Step 1: identify the most likely causes using browser DevTools analysis (LCP, CLS, FID, JS bundle size, render blocking). - Step 2: for each cause, provide the fix with code. - Step 3: implement Core Web Vitals improvements (LCP, CLS, INP). - Step 4: set up performance monitoring and regressions alerts. - Step 5: prioritise by user-perceived impact. # Goal Cause diagnosis by DevTools metrics, fixes with code, Core Web Vitals improvements, monitoring setup, and user-impact prioritisation. # Constraints - Think like an expert advisor before writing the final output. - Ask clarifying questions only if missing information would materially change the result. - Avoid generic filler, vague advice, and unsupported claims. - Make the output specific, practical, and ready to use. # Output Cause diagnosis by DevTools metrics, fixes with code, Core Web Vitals improvements, monitoring setup, and user-impact prioritisation.
{{double-curly}} with your real context.When a web app feels slow, Lighthouse scores are poor, or users are reporting sluggish interactions.
Image optimisation alone typically improves LCP by 30–60% — compress, use modern formats (WebP/AVIF), and add loading='lazy' before optimising JavaScript.
Debug this problem systematically. Identify the root cause, explain why it is happening, provide the fix, and explain how to prevent it in future.
Design the high-level architecture for this system. Cover components, data flow, scaling strategy, and key design decisions.
Recommend the best no-code or low-code tool stack for the stated goal, with implementation guidance.
Design the complete analysis approach for the stated question. Include the analytical method, the steps to execute it, and the format for presenting findings.