This skill should be used when the user is building or reviewing loading states, optimistic UI updates, skeleton screens, code splitting, lazy loading, or performance budgets. Covers perceived speed, bundle size optimization, INP targets, and any work where application responsiveness and perceived latency matter.
npx claudepluginhub oborchers/fractional-cto --plugin saas-design-principlesThis skill uses the workspace's default tool permissions.
Speed is not an optimization — it is the product. Linear built a billion-dollar company on this insight. Every architectural decision should serve Nielsen's three perception thresholds.
Generates design tokens/docs from CSS/Tailwind/styled-components codebases, audits visual consistency across 10 dimensions, detects AI slop in UI.
Records polished WebM UI demo videos of web apps using Playwright with cursor overlay, natural pacing, and three-phase scripting. Activates for demo, walkthrough, screen recording, or tutorial requests.
Delivers idiomatic Kotlin patterns for null safety, immutability, sealed classes, coroutines, Flows, extensions, DSL builders, and Gradle DSL. Use when writing, reviewing, refactoring, or designing Kotlin code.
Speed is not an optimization — it is the product. Linear built a billion-dollar company on this insight. Every architectural decision should serve Nielsen's three perception thresholds.
| Threshold | Perception | Target For |
|---|---|---|
| 100ms | Instantaneous — feels caused by the user | Toggles, selections, navigating between loaded views |
| 1 second | Flow uninterrupted — user feels in control | Page transitions, data loads |
| 10 seconds | Attention limit — user wants to multitask | Show percent-done indicator or lose them |
The UI must respond before the server confirms. This does not require a local-first architecture — it requires separating the feedback loop from network latency.
Update the UI immediately on user action. Reconcile with the server in the background.
When to use optimistic updates:
Rules:
Skeleton screens beat spinners, but only when done correctly.
Research findings (Bill Chung):
When to use which loading indicator:
| Load Duration | Indicator |
|---|---|
| < 1.5 seconds | Nothing, or a subtle spinner |
| 1.5–10 seconds | Skeleton screen with shimmer |
| > 10 seconds | Percent-done progress bar |
Enforce concrete budgets, not aspirational goals.
Bundle budget: Total JavaScript under 200KB gzipped. Code-split by route. Lazy-load modals, charts, and non-critical UI.
Responsiveness budget: INP (Interaction to Next Paint) must stay at or below 200ms. This measures responsiveness across all interactions, not just page load. Keep main-thread tasks under 50ms. Break long operations with requestAnimationFrame or scheduler.yield().
Working implementations in examples/:
examples/optimistic-update.md — Toggle-favorite pattern with rollback in React, Vue, and Svelteexamples/skeleton-screen.md — Shimmer CSS and skeleton components matching content layoutexamples/code-splitting.md — Route-level splitting and lazy-loading in React, Vue, and SvelteKitWhen reviewing existing code for speed: