Intermediate interview questions in Frontend Dev, page 14
How do React Profiler flame and ranked charts pinpoint bottlenecks?
Flame chart width and color show duration with children; ranked chart sorts by self-time to surface the top component.
How to implement a derived Redux slice performantly and maintainably?
This tests minimal state and memoized selector design. Use Reselect's createSelector to compute data from multiple slices, keeping state minimal and avoiding redundant work. A red flag is storing derived values in Redux or recalculating without memoization.
Explain the difference between Server and Client Components in Next.js
Server components run on the server with no client JS and access backends directly; client components ship JS and handle state.
What is the Virtual DOM and why does React use it?
This tests reconciliation as declarative abstraction, not raw speed. Good answers define VDOM as in-memory UI synced to the real DOM, explain declarative state mapping, and note fibers enable incremental rendering.
How do you ensure a complex form is fully accessible?
Pair labels to inputs, move focus to first error on submit, and link aria-invalid to aria-describedby.
What drives your choice between Zustand and Redux Toolkit at scale?
What it tests: matching state philosophy to constraints, not hype. Outline: weigh Zustand's minimal footprint against Redux Toolkit's DevTools and structured async patterns. Red flag: claiming one is always better regardless of team size or debugging needs.
How do you manage database connections in serverless Next.js API routes?
This tests serverless concurrency and connection limits. A strong answer notes lambda scaling exhausts DB connections, advocates connection pooling or serverless drivers, and caches the client globally.
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