Top 10 Interview Questions for Intermediate Full Stack Engineers

Master these essential interview questions to showcase your full stack expertise. Each answer is crafted to demonstrate both technical depth and practical experience.

1. Explain Your Approach to Database Design and Optimization

Best Answer: "I follow a systematic approach starting with proper normalization and indexing strategies. First, I analyze the application's data requirements and access patterns. For normalization, I typically aim for 3NF while being pragmatic about denormalization when performance requires it. I use tools like EXPLAIN ANALYZE to identify bottlenecks and implement solutions such as:

Strategic indexing based on query patterns
Partitioning for large tables
Materialized views for complex aggregations
Query optimization through proper JOIN strategies

In a recent project, this approach reduced our average query time from 2.5s to 150ms."

2. How Do You Handle Authentication and Security in Full Stack Applications?

Best Answer: "I implement security in layers, starting with HTTPS for all communications. For authentication, I prefer JWT with refresh tokens stored in HTTP-only cookies. I implement rate limiting, CSRF protection, and input validation on both client and server sides. For password storage, I use strong hashing algorithms like bcrypt with proper salt rounds. I also follow the principle of least privilege for API endpoints and implement role-based access control (RBAC). Regular security audits and keeping dependencies updated are crucial parts of my security strategy."

3. Describe Your Experience with Microservices Architecture

Best Answer: "I've worked with both monolithic and microservices architectures. In microservices, I focus on:

Service boundaries based on business domains
Inter-service communication using both REST and message queues
API gateways for request routing and aggregation
Circuit breakers for fault tolerance
Distributed tracing for debugging

I use Docker for containerization and Kubernetes for orchestration. I've implemented event-driven patterns using RabbitMQ for asynchronous communication between services."

4. What's Your Strategy for Frontend Performance Optimization?

Best Answer: "I approach frontend performance holistically:

Code splitting and lazy loading using dynamic imports
Efficient state management with local state where possible
Resource optimization (images, fonts, third-party scripts)
Implementing proper caching strategies
Using performance budgets and monitoring Core Web Vitals

I use tools like Lighthouse and Chrome DevTools for profiling. Recently, I reduced our First Contentful Paint from 2.8s to 0.9s by implementing proper code splitting and optimizing the critical rendering path."

5. How Do You Handle API Design and Documentation?

Best Answer: "I follow REST principles and use OpenAPI (Swagger) for documentation. My API design process includes:

Consistent naming conventions and resource hierarchy
Proper HTTP method usage and status codes
Versioning strategy (typically URI versioning)
Comprehensive error handling and validation
Rate limiting and pagination implementation

I maintain living documentation that auto-generates from code annotations, ensuring docs stay current with the implementation."

6. Explain Your Testing Strategy Across the Stack

Best Answer: "I implement a comprehensive testing pyramid:

Unit tests for business logic (80% coverage target)
Integration tests for API endpoints and database operations
E2E tests for critical user flows
Performance tests for high-traffic endpoints

I use Jest for JavaScript testing, Cypress for E2E, and k6 for load testing. I emphasize testing business-critical paths and edge cases, with CI/CD integration ensuring all tests pass before deployment."

7. How Do You Approach State Management in Complex Applications?

Best Answer: "I choose state management solutions based on application needs:

Local component state for isolated UI state
React Context for shared UI state
Redux/Zustand for complex global state
Server state management with react-query/SWR

I follow principles like single source of truth and immutability. For larger applications, I implement domain-driven state organization with proper action/reducer patterns."

8. Describe Your Experience with CI/CD and DevOps Practices

Best Answer: "I implement automated pipelines using tools like GitHub Actions or GitLab CI. My typical pipeline includes:

Automated testing and linting
Security scanning (SAST/DAST)
Docker image building and scanning
Infrastructure as Code using Terraform
Blue-green deployments for zero downtime

I emphasize monitoring and observability using tools like Prometheus and Grafana, with automated alerting for critical issues."

9. How Do You Handle Scalability and High Traffic?

Best Answer: "I approach scalability through:

Horizontal scaling with load balancing
Caching strategies (Redis, CDN)
Database optimization and replication
Asynchronous processing for heavy tasks
Resource pooling and connection management

I've implemented auto-scaling based on metrics like CPU usage and request latency. For high traffic, I use techniques like database sharding and implement circuit breakers to prevent cascade failures."

10. What's Your Approach to Code Quality and Maintenance?

Best Answer: "I maintain code quality through:

Consistent coding standards (ESLint, Prettier)
Regular code reviews and pair programming
Documentation of complex logic and architectural decisions
Technical debt tracking and regular refactoring
Monitoring and addressing code smells

I use tools like SonarQube for static analysis and maintain high test coverage. Regular dependency updates and security patches are part of our maintenance routine."