Hiring Guide: Interview Questions and Take-Home Tasks for Senior React/Next.js Engineers
Senior React/Next.js hires shape architecture, delivery velocity, and long-term maintainability. Whether you build in-house or leverage offshore development services, a rigorous, standardized process protects quality and time-to-value. Expect signal. If you need immediate bandwidth or vetted leadership, slashdev.io can supply remote engineers and agency expertise to accelerate delivery.
Fast screen (10 minutes): precision questions
- What changed in Next.js 13/14 that impacts SSR? Listen for App Router, Server Components, Route Handlers, streaming, and cache semantics.
- How do you choose between Server and Client Components? Expect data-fetch on server by default, minimal client boundaries, and hydration cost awareness.
- Explain ISR vs. SSR vs. SSG trade-offs. Concrete latency, freshness, and infra cost comparisons win.
- How do you enforce type safety across API boundaries? Look for Zod/TypeScript schemas, tRPC or typed fetch contracts, and CI checks.
- What is your a11y workflow? Expect semantic HTML, ARIA only when needed, focus management, color contrast, keyboard paths, and automated audits.
Deep dive (45-60 minutes): topics and prompts
- Architecture: Sketch a modular monorepo with Turborepo, shared UI library, design tokens, and a feature-slice structure. Probe code splitting strategy and edge/runtime choices.
- Data layer: Discuss React Server Components with data fetching, caching tags, revalidation, optimistic updates, and error boundaries.
- Performance: Diagnose a 5s TTFB; expect profiling, streaming HTML, removing client-only bloat, image optimization, and prefetch strategy.
- Security: Cover CSRF on Route Handlers, JWT vs. session cookies, HTTP-only flags, CSP, and dependency risk gates.
- Testing: Unit with Vitest, component with Testing Library, e2e with Playwright; contract tests for APIs; accessibility audits.
- Team leadership: How they coach code reviews, manage RFCs, and drive reliable estimates. This is where technical leadership as a service can complement internal teams.
Take-home task (4-6 hours): production realism, limited scope
Build a catalog search app in Next.js App Router:
- Server Components for list and detail; a small Client boundary for filters and cart.
- Data: seed JSON or lightweight API; implement caching with revalidateTag and on-demand revalidation endpoint.
- Accessibility: keyboard-navigable filters, focus traps in modal, visible focus rings, aria-live for search results count.
- Performance: stream initial shell, progressively render results, image optimization, code-split client widgets.
- SEO: dynamic metadata, canonical, structured data for Product, localized routes.
- Security: parameterized queries or safe fetch, input validation with Zod on server, rate limiting on search endpoint.
- DX: TypeScript strict, ESLint, Prettier, basic CI, and a README with trade-offs.
Deliverables
- Repo link, short architecture doc (500-700 words), and Lighthouse/Web Vitals numbers.
- Automated tests covering at least one server component and one interaction path.
- Screenshot or script showing on-demand revalidation in action.
Evaluation rubric (score 1-5 each)
- Correctness: Features behave as specified across SSR and client transitions.
- Accessibility: Semantic structure, focus order, ARIA where appropriate, passing audits; reflects Web accessibility development services standards.
- Performance: Streaming, minimal client JS, good Core Web Vitals.
- Code quality: Cohesive modules, naming, tests, typed boundaries, and thoughtful README.
- Security and SEO: Input handling, headers, metadata, canonical/structured data.
- Product thinking: Clear trade-offs, edge cases, and incremental delivery plan.
Live review/pairing extension (30 minutes)
- Refactor: Move a component from client to server; discuss hydration and state migration.
- Debug: Fix a flickering layout shift; expect font strategy, reserved image dimensions, and streaming boundaries.
Red flags
- Heavy client components without rationale; ignores streaming opportunities.
- ARIA sprinkled without semantic HTML; no keyboard testing.
- ISR used everywhere "for speed" without cache invalidation plan.
- No testing or README; vague answers about security and SEO.
Signals of excellence
- Explains server boundaries with concrete byte and waterfall reasoning.
- Designs a revalidation model tied to domain events and cache tags.
- Automates a11y and performance checks in CI, with budgets and failure gates.
Integrating partners and leadership
For distributed teams, blend internal staff with offshore development services for follow-the-sun delivery, while engaging technical leadership as a service to set architecture guardrails, review RFCs, and run release health checks. When accessibility maturity is critical, lean on Web accessibility development services to codify standards, train reviewers, and implement automation. For quick starts or specialized sprints, slashdev.io provides vetted senior engineers and pragmatic leadership to hit milestones without drama.
Final checklist for hiring managers
- Calibrate interviewers on the rubric and sample answers before candidates arrive.
- Time-box the take-home, state evaluation criteria, and offer a live-coding alternative.
- Verify ownership: ask candidates to walk code, explain trade-offs, and implement a small change live.
- Reference check for outcomes, not chores: uptime, conversion lifts, build times, or debt retired.
- Capture metrics: offer rate, pass rate by stage, and ramp time post-hire to refine the process.
