Backend architecture defines how server-side systems are structured, organized, and scaled to handle business logic, data processing, and service orchestration. From traditional monoliths to distributed microservices, each architectural pattern represents trade-offs between simplicity, scalability, team independence, and operational complexity. Choosing the right architecture depends on team size, deployment frequency, performance requirements, and how much complexity your organization can effectively manage — there's no universal "best" architecture, only the one that fits your current constraints and enables your team to deliver value efficiently.