app-performancelisted

# Shopify Embedded App Performance Fix slow Shopify embedded apps before Built for Shopify rejects them, merchants uninstall, and Shopify demotes you in App Store search. The Web Vitals are the gate. Everything below is how you walk through it. --- ## 1. When to use this skill Trigger this skill when: - `shopify app dev` runs but the embedded iframe takes 4+ seconds to render - BFS review comes back "fails performance" with no specifics - Lighthouse on your admin route scores below 70 - Web Vitals API reports LCP > 2.5s, INP > 200ms, or CLS > 0.1 over 28 days - Your bundle is > 500KB gzipped and you don't know why - GraphQL queries are returning `THROTTLED` (as 200 OK, not 429) - Prisma queries take 800ms+ in production but 40ms locally - Webhook handlers are taking > 2 seconds and triggering Shopify retries - A merchant DMs you "your app is the slowest thing in my admin" - You're about to submit for Built for Shopify and want to pass on the first try Don't use this skill for storefront / theme performance — that's a different problem (theme app extensions, web pixels, checkout extensions). This skill is about the admin embedded surface and the server behind it. --- ## 2. Built for Shopify performance thresholds (current) These are the exact numbers. Memorize them. ### Core Web Vitals (admin, measured via App Bridge Web Vitals API) | Metric | Threshold | Measurement window | Min sample size | |--------|-----------|--------------------|-----------------| | **LCP** (