The core of service-oriented architecture is centralized governance over how diverse services provide their capabilities and communicate.

This idea lead to the Enterprise Service Bus (ESB) — a central integration layer connecting all services, handling:

• protocol conversion
• message translation into enterprise-wide data models
• request routing
• security rules for all services (auth, rate limiting, access control)
• centralized logging and auditing
• workflow orchestration, including cross-service transactions and compensations

ESB made sense in heterogeneous enterprise environments — but it also concentrated complexity and control in one place. Many of today’s architectural advancements are reactions to this tradeoff.