1. How do you collaborate with backend teams to design APIs that meet the needs of a React frontend?
I start by aligning on use cases and data needs via API contracts or OpenAPI specs. I advocate for:
- REST or GraphQL depending on complexity
- Consistent resource structures
- Pagination, filtering, and sorting support
We use Postman/Swagger for early mocks and shared API design docs . I emphasize frontend-first thinking : minimize over-fetching and support real-time or lazy-loading if needed.
2. What’s your approach to handling API versioning in a React app when the backend evolves?
Answer:
I prefer URL-based versioning (e.g., /v1/users) for clarity and cacheability. In React:
- Encapsulate API logic in services:
// api/user.ts
export const fetchUser = () => axios.get("/v2/user");
- Use feature flags or environment-based toggles to migrate gracefully
- Track version drift with integration tests
3. How do you design a React frontend to handle inconsistent or poorly documented backend APIs?
Answer:
To mitigate risk:
- Use TypeScript with runtime validators like
zod or io-ts:
const UserSchema = z.object({ id: z.string(), name: z.string() });
- Abstract API responses via adapters to normalize data:
const mapUser = (data) => ({ id: data.user_id, name: data.full_name });
- Document and flag inconsistencies for backend refactoring
Answer:
- Request only needed fields (
fields=name,email or GraphQL selection sets)
- Paginate lists to reduce load:
axios.get('/users?page=2&limit=10');
- Compress responses (Gzip/Brotli) and cache where possible
- Use server-driven sorting/filtering to avoid client-side overhead
5. How do you integrate real-time APIs (e.g., WebSockets, Server-Sent Events) into a React app?
Answer:
- Use WebSocket for bi-directional data:
useEffect(() => {
const socket = new WebSocket("wss://example.com/socket");
socket.onmessage = (event) => updateState(JSON.parse(event.data));
}, []);
- Use context or Zustand to share state updates
- For SSE: use
EventSource, but fall back to polling if needed
- Clean up sockets on unmount to prevent memory leaks
6. What’s your approach to mocking APIs during React development when the backend isn’t ready?
Answer:
- Use Mock Service Worker (MSW) to intercept real
fetch/axios:
rest.get('/api/user', (req, res, ctx) => res(ctx.json({ name: 'Test' })));
- Mirror backend contract using JSON mocks or Swagger
- Toggle mock mode via
NODE_ENV or dev flag
- Mock at the network level to test integration, not logic
7. How do you handle rate-limited APIs in a React app without degrading user experience?
Answer:
- Implement exponential backoff or
Retry-After headers handling
- Queue or debounce high-frequency requests:
const debouncedSearch = debounce(fetchSuggestions, 300);
- Show UI feedback (e.g., spinners, retry buttons)
- Cache frequent responses locally when possible (e.g.,
react-query, SWR)
8. What’s your process for debugging frontend-backend integration issues in a React app?
Answer:
- Check network tab (status codes, headers, body)
- Use
console.error or error boundaries for visibility
- Validate API types using schemas
- Log and compare frontend request with backend expectations
- Use
Postman or curl to isolate backend issues
Collaborate closely with backend engineers, ideally in real-time debugging sessions.
Answer:
- Provide user-centric scenarios showing impact (e.g., slow loads, poor UX)
- Suggest standards like
limit, offset, sort, filter query params
- Emphasize mobile performance and data granularity
- Use shared API specs or examples to bridge gaps
10. How do you train a frontend team to work effectively with backend engineers on a React project?
Answer:
- Introduce API design-first mindset (e.g., OpenAPI, GraphQL schema-first)
- Define clear contracts and use tools like MSW for development
- Encourage joint reviews of API designs
- Set up consistent conventions (e.g., service abstraction, error handling)
- Promote empathy-driven collaboration by having both sides participate in each other’s demos and retros