Next.js Interview Questions: Basic to Advanced

1What problems does Next.js solve that React alone does not, and what does it deliberately leave to React?Basicconceptual40 min
2Walk through what create-next-app generates and what each top-level file and folder is responsible for.Basicconceptual40 min
3How does the App Router differ from the Pages Router, and what would make you keep an app on Pages?Basicconceptual45 min
4Trace what happens between next dev, next build, and an incoming production request.Basicconceptual45 min
5Explain the difference between static, dynamic, and streamed rendering in Next.js and how a route ends up in each.Intermediateconceptual50 min
6What do src/app, public, the env files, and the server-only package each guarantee?Basicconceptual40 min
7You are asked in an interview to justify choosing Next.js for a new product. How do you answer without overselling it?Scenarioscenario25 min
8Check your understanding of the App Router bet, the request cycle, and Next.js conventions.Basicconceptual15 min

9How do folders and page.tsx map onto URL segments in the App Router?Basicconceptual40 minIn writing
10What does a layout persist across navigations, and what actually re-renders when the URL changes?Intermediateconceptual50 minIn writing
11When would you reach for template.tsx instead of layout.tsx?Intermediatepractical45 minIn writing
12Explain route groups, private folders, and colocated files, and when each earns its keep.Intermediatepractical50 minIn writing
13How do dynamic segments, catch-all routes, and generateStaticParams work together?Intermediatepractical55 minIn writing
14What does route segment config still control once Cache Components are in play?Advancedconceptual50 minIn writing
15An interviewer asks you to design the route tree for a multi-tenant dashboard. How do you lay it out?Scenariodesign25 minIn writing
16Check your understanding of segments, layouts, route groups, and dynamic routes.Intermediateconceptual15 minIn writing

17Describe the Server Component mental model: the server tree, client islands, and serialized props.Intermediateconceptual50 minIn writing
18What do "use client" and "use server" actually mark, and why is the boundary a module boundary?Intermediateconceptual50 minIn writing
19What can and cannot be passed from a Server Component to a Client Component, and why?Intermediatepractical55 minIn writing
20How does passing Server Components as children into a Client wrapper keep the client bundle small?Advancedpractical50 minIn writing
21Where are hooks, event handlers, and browser APIs legal, and what error tells you that you crossed the line?Intermediatetroubleshooting45 minIn writing
22How do server-only and tainting stop a secret from reaching the browser by accident?Advancedpractical55 minIn writing
23A teammate has put "use client" at the root layout to fix an error. How do you diagnose and unwind that?Scenariotroubleshooting25 minIn writing
24Check your understanding of the server tree, the client boundary, and what serializes.Intermediateconceptual15 minIn writing

25When should you use Link, and when is a plain anchor the correct choice?Basicpractical40 minIn writing
26Compare useRouter, redirect, notFound, and permanentRedirect, and say where each belongs.Intermediatepractical50 minIn writing
27How do params and searchParams differ between Server and Client Components?Intermediatepractical55 minIn writing
28What does prefetching buy you, what does it cost, and how does the router cache affect freshness?Advancedconceptual55 minIn writing
29What stays mounted across a soft navigation, and how do you use that deliberately?Intermediateconceptual45 minIn writing
30What are the common scroll, focus, and useSearchParams pitfalls on App Router navigations?Advancedtroubleshooting50 minIn writing
31A filter panel writes to searchParams and the page feels sluggish. How do you find and fix the cause?Scenariotroubleshooting25 minIn writing
32Check your understanding of links, router APIs, URL state, and prefetching.Intermediateconceptual15 minIn writing

33How do loading.tsx and Suspense produce a streamed fallback, and where should the boundary sit?Intermediatepractical50 minIn writing
34Compare error.tsx and global-error.tsx, and explain what each can and cannot catch.Intermediatepractical50 minIn writing
35What is the difference between not-found.tsx and calling notFound()?Intermediateconceptual40 minIn writing
36What problem do parallel routes and slots solve that nested layouts cannot?Advanceddesign60 minIn writing
37How do intercepting routes give a modal a real, shareable URL?Advanceddesign60 minIn writing
38How do default.tsx, catch-all recovery, and nested error UI interact on a complex route?Advancedtroubleshooting50 minIn writing
39Design the loading and error strategy for a dashboard with three independently slow panels.Scenariodesign25 minIn writing
40Check your understanding of loading, error, not-found, parallel, and intercepting routes.Intermediateconceptual15 minIn writing

41Why is an async Server Component the primary data-fetching API in the App Router?Intermediateconceptual50 minIn writing
42How do fetch request memoization and React.cache stop duplicate work in one render?Advancedconceptual55 minIn writing
43How do you spot a data waterfall, and when is Promise.all the wrong fix?Advancedtroubleshooting55 minIn writing
44What happens to a route when you read cookies or headers, and how do you contain that?Intermediatepractical50 minIn writing
45How do you use Suspense to stream a slow subtree without holding up the whole page?Advancedpractical55 minIn writing
46When must the browser do the fetching, and how do you keep that path small?Intermediatepractical45 minIn writing
47A product page takes 3 seconds because of chained fetches. Walk through your diagnosis and fix.Scenariotroubleshooting25 minIn writing
48Check your understanding of server fetching, memoization, waterfalls, and streaming.Advancedconceptual15 minIn writing

49Why did Next.js flip to uncached-by-default, and what broke in the old mental model?Advancedconceptual50 minIn writing
50Explain "use cache", cacheLife, and cacheTag, and how they compose.Advancedpractical60 minIn writing
51How does Partial Prerendering serve a static shell with dynamic holes?Advancedconceptual60 minIn writing
52When do you reach for revalidateTag versus updateTag?Advancedpractical55 minIn writing
53What cannot go inside a "use cache" boundary, and why is that restriction there?Advancedconceptual50 minIn writing
54A page shows stale data. How do you work out which cache layer you are hitting?Scenariotroubleshooting55 minIn writing
55Design the caching strategy for a catalog with 50,000 products and hourly price updates.Scenariodesign25 minIn writing
56Check your understanding of cache components, revalidation, and PPR.Advancedconceptual15 minIn writing

57What is a Server Action at the wire level, and what does that imply for how you treat it?Intermediateconceptual50 minIn writing
58How does binding an action to a form's action prop keep the form working without JavaScript?Intermediatepractical45 minIn writing
59How do useActionState and useFormStatus give you pending and result UI?Intermediatepractical55 minIn writing
60How do you validate FormData on the server and return usable field-level errors?Intermediatepractical55 minIn writing
61Why must every Server Action authenticate and authorize independently?Advancedpractical50 minIn writing
62How do you combine useOptimistic with revalidation so the UI never lies for long?Advancedpractical60 minIn writing
63An action updates a row but the list does not refresh. Walk through the causes you would check.Scenariotroubleshooting25 minIn writing
64Check your understanding of Server Actions, forms, pending UI, and mutation safety.Intermediateconceptual15 minIn writing

65When does a route handler beat a Server Action, and when is it the wrong tool?Intermediatedesign50 minIn writing
66How do you receive a signed webhook correctly, including the raw body problem?Advancedpractical55 minIn writing
67How do you set cookies, shape NextResponse, handle CORS, and stream from a route handler?Intermediatepractical55 minIn writing
68How do you design and version a public JSON API inside a Next.js app?Advanceddesign45 minIn writing
69How do you accept a file upload safely on the server, and where do the size limits actually apply?Advancedpractical50 minIn writing
70How do rate limits, auth headers, and a stable error shape keep an API safe to expose?Advancedpractical50 minIn writing
71Design the endpoint that receives your payment provider's webhooks. What must be true of it?Scenariodesign25 minIn writing
72Check your understanding of route handlers, webhooks, uploads, and API safety.Intermediateconceptual15 minIn writing

73When do you use the static metadata export versus generateMetadata?Basicpractical45 minIn writing
74How do titles, descriptions, canonicals, and robots directives fit together on a real site?Intermediatepractical50 minIn writing
75How do you produce correct Open Graph and Twitter cards, including generated OG images?Intermediatepractical55 minIn writing
76What do sitemap.ts, robots.ts, and manifest.ts each generate, and when do they run?Intermediatepractical45 minIn writing
77How do you add JSON-LD structured data without describing something the page does not contain?Advancedpractical50 minIn writing
78How do you keep preview deployments, trailing slashes, and duplicate URLs from damaging indexing?Advancedtroubleshooting50 minIn writing
79A marketing site's pages are indexed with the wrong titles. How do you find and fix it?Scenariotroubleshooting25 minIn writing
80Check your understanding of metadata, social previews, and indexing controls.Intermediateconceptual15 minIn writing

81How do next/image's sizes, priority, and remote patterns affect LCP and layout shift?Intermediatepractical55 minIn writing
82How does next/font eliminate the font-driven layout shift that a link tag causes?Intermediatepractical45 minIn writing
83How do you load a third-party script without paying for it on first paint?Intermediatepractical45 minIn writing
84Compare CSS Modules, global CSS, and Tailwind in the App Router.Basicdesign50 minIn writing
85When should an asset live in public/, be imported, or be served from a CDN?Basicdesign40 minIn writing
86What breaks for keyboard and screen-reader users on client-side route changes, and how do you fix it?Advancedpractical50 minIn writing
87A page scores badly on CLS and LCP. Walk through what you would check in a Next.js app.Scenariotroubleshooting25 minIn writing
88Check your understanding of images, fonts, scripts, styling, and route accessibility.Intermediateconceptual15 minIn writing

89How do you choose between httpOnly session cookies and client-readable tokens?Intermediatedesign50 minIn writing
90What should proxy.ts do, and what must never be decided there?Advanceddesign55 minIn writing
91Why must Server Components, Server Actions, and route handlers each check auth themselves?Advancedpractical55 minIn writing
92What CSRF exposure do Server Actions have, and what closes it?Advancedpractical50 minIn writing
93How do NEXT_PUBLIC_ prefixes, server-only, and bundling rules decide what leaks?Intermediatepractical45 minIn writing
94Walk through an OAuth and a magic-link flow in the App Router, including the state and PKCE parts.Advanceddesign60 minIn writing
95An auth check lives only in middleware. Explain the exposure and how you would close it.Scenariotroubleshooting25 minIn writing
96Check your understanding of sessions, the proxy, CSRF, and secret handling.Advancedconceptual15 minIn writing

97How would you choose between Prisma, Drizzle, and raw SQL for a new Next.js app?Intermediatedesign50 minIn writing
98Why put database access behind a server-only data module instead of calling it from components?Advanceddesign50 minIn writing
99What goes wrong with database connections on serverless, and how do you fix it?Advancedtroubleshooting55 minIn writing
100How do you turn a unique-constraint violation into a good user-facing error?Advancedpractical50 minIn writing
101How do you paginate and cache a list page correctly with "use cache"?Advancedpractical55 minIn writing
102How do migrations, seeds, and local-versus-production databases fit into a deploy?Intermediatepractical45 minIn writing
103Your app exhausts database connections under load on Vercel. Diagnose it.Scenariotroubleshooting25 minIn writing
104Check your understanding of the server data layer, pooling, transactions, and migrations.Advancedconceptual15 minIn writing

105How do LCP, INP, and CLS each fail in a Next.js app, and what fixes each?Advancedtroubleshooting50 minIn writing
106What does a "use client" boundary actually cost, and how do you measure it?Advancedpractical55 minIn writing
107How does Suspense placement decide whether streaming helps or hurts?Advanceddesign55 minIn writing
108What does the React Compiler do for you, and where does manual memoisation still matter?Advancedconceptual50 minIn writing
109Why is the Node.js runtime the default recommendation, and how do you migrate a legacy edge route?Advancedpractical50 minIn writing
110How do you get useful production logs, traces, and error tracking out of a Next.js app?Advancedpractical50 minIn writing
111Traffic tripled and INP regressed. Walk through your investigation.Scenariotroubleshooting25 minIn writing
112Check your understanding of web vitals, bundles, streaming, and runtimes.Advancedconceptual15 minIn writing

113How do you choose between locale in the URL, a cookie, or the Accept-Language header?Intermediatedesign50 minIn writing
114How do you handle translated messages, locale-aware dates, and hreflang correctly?Intermediatepractical55 minIn writing
115How do you wire MDX and frontmatter into the App Router as typed content?Intermediatepractical55 minIn writing
116How does draft mode give editors a preview without leaking unpublished content?Advancedpractical50 minIn writing
117How do you statically generate a catalog too large to build all at once?Advanceddesign50 minIn writing
118When do you use redirects, rewrites, and next.config rules on a content site?Intermediatepractical45 minIn writing
119Design the routing and caching for a documentation site in six languages.Scenariodesign25 minIn writing
120Check your understanding of locales, MDX, draft mode, and large-catalog generation.Intermediateconceptual15 minIn writing

121How do you split testing between unit tests, Playwright, and RSC-aware tests?Advanceddesign55 minIn writing
122How do you test Server Actions, route handlers, and authenticated paths?Advancedpractical60 minIn writing
123What do preview deployments and environment scoping give you, and where do they mislead?Intermediatepractical45 minIn writing
124What does self-hosting a Next.js app on Node or Docker require that Vercel hid from you?Advanceddesign60 minIn writing
125What belongs on a production checklist for headers, CSP, caching, and backups?Advancedpractical55 minIn writing
126Design and defend a complete production Next.js application end to end.Scenariodesign240 minIn writing
127How would you convince a sceptical reviewer that your Next.js app is production-ready?Scenarioscenario25 minIn writing
128Check your understanding of testing strategy, deployment, and production readiness.Advancedconceptual15 minIn writing