What is the purpose of the `useContext` hook in React?

0-2 years experience

1. 1We have a ThemeContext that provides 'dark' or 'light'. How would you use useContext inside a Button component to apply the correct CSS class?
2. 2If you forget to wrap a component tree with the corresponding Provider, what does useContext return?
3. 3Can you show a minimal example of creating a LanguageContext and consuming it with useContext in a functional component?

2-5 years experience

1. 1Our feature‑toggle context was updated with a new flag, but the UI isn’t reflecting the change. Walk me through how you would debug this issue.
2. 2We need to share a WebSocket connection across many components via context. How would you structure the provider and consumers, and what trade‑offs should you consider?
3. 3A form component reads and writes shared form state through context. How would you prevent unrelated fields from re‑rendering when only one field changes?

5-8 years experience

1. 1In a dashboard with dozens of widgets reading from a global SettingsContext, users notice lag when a single setting changes. How would you redesign the context usage to improve performance?
2. 2We have nested contexts for Auth, Theme, and Locale. How do you decide the order of Providers, and what impact does that order have on useContext consumers?
3. 3A legacy class component needs a value from a context used in a functional component tree. How would you bridge that gap without refactoring the entire tree?

8+ years experience

1. 1Our monolith is being split into micro‑frontends, each with its own context but also needing shared authentication state. How would you design a cross‑micro‑frontend context strategy and what pitfalls would you watch for?
2. 2A shared component library relies on a global context that is being deprecated. How would you plan the migration to a new context or state‑management approach while minimizing breaking changes for downstream teams?
3. 3When scaling to thousands of concurrent users, how does useContext interact with server‑side rendering and hydration, and what patterns can mitigate any performance or consistency issues?