Describe default.js.

0-2 years experience

1. 1If you add a file called about.js under pages, what does Next.js do with the default export inside it?
2. 2What happens if you forget to export a component as default from a page file?
3. 3How would you create a simple homepage using pages/index.js and its default export?

2-5 years experience

1. 1You notice that navigating to /profile returns a 404 even though pages/profile.js exists. The file exports a named component but not default. How would you fix it?
2. 2When adding getStaticProps to a page, why must the component still be the default export?
3. 3If you want to lazy‑load a child component inside a page, does the default export affect the bundle size or loading behavior?

5-8 years experience

1. 1In a large Next.js app, some teams use named exports for page components, causing routing failures. How would you enforce the default‑export convention across the repo and what trade‑offs does that introduce?
2. 2Discuss the performance implications of placing heavy data‑fetching logic inside the default exported component versus extracting it to a separate module.
3. 3When migrating a legacy React app to Next.js, you have files that export multiple components. How do you restructure them so routing works correctly?

8+ years experience

1. 1Your organization runs several micro‑frontends built on Next.js and wants a unified linting and CI pipeline to guarantee every page file has a proper default export. How would you design that system at scale?
2. 2You need to serve two variants of a page based on feature flags, but Next.js still requires a single default export for routing. How would you architect the solution while keeping the default‑export contract intact?
3. 3Consider a monorepo where shared UI components are versioned independently. How do you manage default‑export compatibility across teams when upgrading Next.js versions?