A subdomain boundary heuristic helps identify where one business subdomain ends and another begins. These boundaries can shape team responsibilities and parts of the software architecture. Heuristics are starting points, not rules: compare several and adapt them to the context. section 9.3.2
Two ways to test a candidate boundary are:
- Map a process or user journey into steps. Treat each step as a candidate subdomain when it is largely self-contained and shares few concepts with other steps. section 9.3.2
- Look across steps and journeys for recurring concepts. Consider a dedicated subdomain when keeping those concepts separate would make duplication too costly. section 9.3.2
An e-commerce journey
Placing an order can suggest Search and Browse, Product Details, Cart and Checkout, and Reviews as candidate subdomains. Reviews may be a strong boundary if it needs little from elsewhere beyond product and customer IDs, leaving it relatively insulated from changes to Customer and Order concepts. section 9.3.2
