Design and develop secure, scalable, reliable, and efficient backend services. Collaborate with frontend developers to define API endpoints and data contracts. Design and optimize database schemas and write performant SQL queries. Integrate third-party services, libraries, and tools. Apply security best practices. Improve code quality, performance, and maintainability. Write comprehensive unit, integration, and end-to-end tests. Debug and troubleshoot issues. Participate in code reviews. Document code, APIs, and system architecture. Set up and maintain CI/CD pipelines.