The Key NextJS Interview Questions that Matter the Most

64. How do you set up end-to-end testing for Next.js?

Answer: Use Playwright or Cypress for E2E testing. Configure test environments, implement page object models, and set up CI/CD integration for automated testing.

Ideal candidate should discuss: Testing strategies, environment setup, and test data management.

65. Implement API route testing in Next.js
Answer: Use Jest with supertest for API route testing. Mock external dependencies and test different scenarios including error cases.
import handler from '../pages/api/users';
import { createMocks } from 'node-mocks-http';
describe('/api/users', () => {
  it('returns users list', async () => {
    const { req, res } = createMocks({ method: 'GET' });
    await handler(req, res);
    expect(res._getStatusCode()).toBe(200);
  });
});

Ideal candidate should discuss: Test organization, mocking strategies, and coverage requirements.

66. How do you test server-side rendering in Next.js?

Answer: Test SSR by checking rendered HTML content, data fetching functions, and ensuring proper hydration. Use testing libraries that support server-side rendering.

Ideal candidate should discuss: SSR testing challenges, hydration testing, and performance testing.

67. How do you handle large datasets in Next.js applications?

Answer: Implement pagination, virtualization for large lists, streaming data, and efficient data fetching strategies. Use database optimization and caching for better performance.

Ideal candidate should discuss: Data processing strategies, memory management, and performance optimization.

68. Implement data transformation pipelines in Next.js

Answer: Create API routes for data processing, use streaming for large datasets, implement background jobs for heavy processing, and cache transformed data.

Ideal candidate should discuss: Data processing patterns, error handling, and scalability considerations.

69. How do you integrate Next.js with data visualization libraries?

Answer: Use libraries like D3.js, Chart.js, or Recharts with proper SSR handling. Implement dynamic imports for heavy visualization libraries and optimize rendering performance.

Ideal candidate should discuss: Performance optimization, SSR considerations, and data binding strategies.

70. How do you integrate machine learning models with Next.js?

Answer: Use TensorFlow.js for client-side inference, create API routes for server-side ML processing, implement model caching, and handle large model files efficiently.

Ideal candidate should discuss: Model deployment strategies, performance optimization, and data pipeline integration.

71. Implement real-time AI features in Next.js

Answer: Use streaming responses for AI-generated content, implement WebSocket connections for real-time AI interactions, and handle model inference efficiently.

Ideal candidate should discuss: Streaming implementations, performance optimization, and user experience considerations.

72. How do you handle AI model versioning in Next.js?

Answer: Implement model versioning strategies, A/B test different models, handle graceful model updates, and maintain backward compatibility.

Ideal candidate should discuss: Deployment strategies, testing approaches, and rollback mechanisms.