System Design 101: APIs, Databases, Caching, CDNs, Load Balancing & Production Infra

System design has become a critical skill for software engineers as AI-driven development shifts the focus toward high-level architectural decisions and trade-offs. Effective system design begins with a single-server foundation, scaling horizontally through load balancers—using algorithms like round-robin, least connections, and consistent hashing—to ensure fault tolerance and performance. API design serves as the interface for these systems, with REST, GraphQL, and gRPC offering distinct advantages based on data structure and latency requirements. Security remains paramount, requiring robust authentication methods like JWTs and OAuth2, alongside authorization models such as role-based (RBAC) or attribute-based (ABAC) access control. Protecting these systems involves implementing rate limiting, CORS policies, and input validation to mitigate common vulnerabilities like SQL injection and cross-site scripting, ensuring the development of scalable and secure software architecture.