1. #1

   Mid-levelhooksdesign

   What makes a well-designed custom hook?

   It encapsulates one concern, returns a stable, minimal API, follows the Rules of Hooks, and is composable and independently testable.

2. #2

   Seniorperformancerendering

   What is your systematic approach to fixing slow React renders?

   Profile first, find the bottleneck, then fix the cause — usually unstable props, state placed too high, or large lists — before reaching for memoisation.

3. #3

   Seniorperformancelists

   What is list virtualization and when do you need it?

   Virtualization renders only the visible rows of a long list plus a small buffer, keeping the DOM small and scrolling smooth for thousands of items.

4. #4

   Seniorpatternscomposition

   What is the compound component pattern?

   Related components share implicit state via Context so consumers compose them flexibly, like <Tabs><Tab/></Tabs>, without prop drilling configuration.

5. #5

   Seniorstatearchitecture

   How do you choose between local state, Context, and a state library?

   Use local state by default, Context for low-frequency global values, a server-state library for remote data, and a client store only for complex shared UI state.

6. #6

   Seniorhooksrefs

   What is useImperativeHandle and when is it justified?

   It customises the ref a parent receives, exposing a controlled imperative API (focus, scrollTo) instead of the raw DOM node — used sparingly.

7. #7

   Seniorconcurrentstate

   What is tearing in concurrent React and how is it avoided?

   Tearing is when a single render shows inconsistent values from an external store because rendering was interrupted; useSyncExternalStore prevents it.

8. #8

   Mid-levelerrorsresilience

   How do you design an error-handling strategy with boundaries and Suspense?

   Place granular error boundaries around independent regions, pair them with Suspense for loading states, and handle async/event errors locally.

9. #9

   Mid-levelportalsdom

   What are React portals and when do you use them?

   Portals render children into a different DOM node outside the parent hierarchy while keeping React context and events — ideal for modals and tooltips.

10. #10

    Mid-leveltestingquality

    What is the recommended approach to testing React components?

    Test behaviour from the user’s perspective with React Testing Library — query by role/text, interact, and assert visible output, not implementation details.