Yumin Fish Harvest

Jul 10, 2026 · Fundamentals

Why Aggregates Are So Hard in DDD: Using Invariants to Find Real Boundaries

The article explains that an aggregate is defined by the business invariants that must stay strongly consistent, shows how the aggregate root protects those rules, and provides concrete design principles—ID references, single‑aggregate transactions, small boundaries, validation tests, and common pitfalls—illustrated with an order domain example.