Use this guide to interview a Senior Frontend Engineer. Seniority in frontend shows up as architectural judgment over long-lived codebases, deep web-platform knowledge beneath the framework, and the ability to raise a team's quality bar — not just fluency with the current meta-framework. Pick eight to twelve questions per session, keep the set consistent across candidates, and adapt scenarios to {{Your product or domain}}.

Architecture and frameworks

• How do you architect a frontend codebase for a product where multiple teams ship daily? Which boundaries matter most?
• Walk me through a framework migration or major upgrade you led. How did you keep shipping features during it?
• Micro-frontends: when are they worth their cost? Have you lived with the consequences?
• How do you decide what renders on the server versus the client in a modern framework, and what drives the choice?
• Design the frontend for {{A complex feature such as a real-time collaborative dashboard}}. What are the genuinely hard parts?
• How do you keep a design system healthy across many consumers — versioning, breaking changes, adoption?

What good looks like: senior candidates talk about frontends as long-lived systems shaped by organizational forces — ownership boundaries, migration strategies that never stop the release train, and design-system governance. Be wary of answers that reduce architecture to picking this year's framework.

Web platform and performance

• What happens between a user clicking a link and interacting with the page? Push into the rendering pipeline and hydration.
• How do you diagnose and fix a poor interaction-latency or loading score on a real page?
• How do the caching layers interact — HTTP cache, service worker, CDN? Tell me about debugging them fighting each other.
• When do you move work to a web worker or off the main thread? Give a real example.
• Which recently shipped browser capabilities have changed how you build — container queries, view transitions, or others?
• Beyond code splitting, what has actually worked for you to make a large bundle small?

Accessibility and quality

• How do you make accessibility a team default instead of your personal review burden?
• Walk me through making a complex widget — say a combobox — genuinely accessible, including focus management and screen-reader behavior.
• What testing mix do you run at scale — unit, component, visual, end-to-end — and why that balance?
• How do you prevent regressions in visual polish — spacing, themes, dark mode — without manual QA on every release?
• Tell me about an accessibility issue you found late. What did the fix teach the team?

State and data

• How do you keep server state and client state from tangling? What patterns do you standardize on a team?
• Design robust real-time UI updates — transport choice, reconciliation, conflict handling.
• How do you handle errors across a UI — boundaries, retries, and what the user actually sees?
• Forms at scale: validation, dirty state, autosave. What architecture survives real product complexity?

Technical leadership and mentorship

• How do you review code from engineers stronger in JavaScript than in UX — or the reverse?
• Tell me about raising the frontend quality bar on a team. What resistance did you hit, and what stuck?
• How do you mentor without rewriting people's pull requests?
• A product deadline pressures you to skip accessibility and tests. What do you do, concretely?
• What is your bar for adding a new frontend dependency, and how do you evaluate one with the team?

What good looks like: expect mechanisms, not vibes — lint rules and CI gates that encode the bar, pairing and review habits that teach, documentation that outlives the person. On the deadline question, strong candidates negotiate scope openly and name what ships degraded rather than silently dropping quality.

Product collaboration

• Tell me about pushing back on a design that would have harmed performance or accessibility. How did you land it?
• How do you handle a designer iterating faster than the frontend can absorb?
• When have you shipped a deliberately imperfect UI to learn something? What happened?
• How do you translate business goals into frontend technical priorities?