# Performance

> Performance - Core Web Vitals, bundle size. Use when optimizing speed.

- Skill: `sylphxai/performance` (Agent Skill)
- Install (CLI): `npx skillmds@latest add sylphxai/performance`
- Raw SKILL.md: https://api.skillmd.com/api/skills/sylphxai/performance/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: SylphxAI (https://skillmd.com/u/sylphxai)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/sylphxai/performance

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# Performance Guideline

## Tech Stack

* **Framework**: Next.js (SSR/ISR/Static)
* **Platform**: Vercel
* **Tooling**: Bun

## Non-Negotiables

* Core Web Vitals must meet thresholds (LCP < 2.5s, CLS < 0.1, INP < 200ms)
* Performance regressions must be detectable

## Context

Performance is a feature. Slow products feel broken, even when they're correct. Users don't read loading spinners — they leave. Every 100ms of latency costs engagement.

Don't just measure — understand. Where does time go? What's blocking the critical path? What would make the product feel instant? Sometimes small architectural changes have bigger impact than optimization.

## Driving Questions

* What makes the product feel slow to users?
* Where are the biggest bottlenecks in the critical user journeys?
* What's in the critical rendering path that shouldn't be?
* How large is the JavaScript bundle, and what's bloating it?
* What database queries are slow, and why?
* If we could make one thing 10x faster, what would have the most impact?