Difficulty Distribution
Skills You'll Practice (12)
All 4 Scenarios
Click any scenario to practice it. No account required.
Users Report 'Website Is Slow'
Support is getting flooded with 'website is slow' complaints. But your monitoring shows the API is fast (avg 120ms) and CDN is healthy. You need to identify the cause. You have access to Chrome DevTools, Lighthouse, real user monitoring, and error logs. Walk me through your debugging approach.
React App Bundle Size Ballooned
Your React app bundle went from 400KB to 1.8MB after last week's PRs. First contentful paint (FCP) went from 1.2s to 3.4s. Lighthouse score dropped from 92 to 61. Walk me through how you identify what caused the bloat and fix it.
Design a Design System from Scratch
Your company has 3 product teams building 5 different products. Each has slightly different button styles, colors, and interactions. Leadership wants a unified design system. Walk me through: your approach, technology choices, adoption strategy, and success metrics.
Accessibility Audit Failing
A major client just informed you that your web app fails WCAG 2.1 AA compliance. Their compliance team will audit in 6 weeks. If you don't pass, you lose the contract worth $2M/year. You have 100+ components. Walk me through your remediation plan.