Architecture Tiers CDN (Content Delivery Network) Load Balancing Cache Database Topic Multithreading & Concurrency Microservices Statefulness Scope & Concerns Scalability Consistency Reliability Trade-offs Robustness Availability Performance Extensibility Resiliency Theoretical Topics CAP Theorem Design Patterns SOLID Principles Object-Oriented Design (OOD) Domain-Driven Design (DDD) Singleton Testing Programming Paradigms Test-Driven Development (TDD)