Service-Oriented Architecture (SOA)

SOA exposes business capabilities as services, typically coordinated by an enterprise service bus (ESB) or integration layer. It predates microservices and focuses on integration across heterogeneous systems.

When it fits

• Large enterprises integrating CRM, billing, ERP and legacy systems
• Clear service contracts and governance are required

Risks

• Central ESBs become bottlenecks
• Heavy governance slows delivery if overdone

Real-world examples

• Banks and telcos used SOA with IBM, MuleSoft or TIBCO to orchestrate customer, billing and order flows across many systems
• Government agencies integrate tax, identity and payment systems through service layers with strict contracts

Practical tips

• Avoid over-centralising logic in the ESB; keep services cohesive
• Treat contracts as products with versioning and lifecycle management