10: Aggregates

Definition:

A cluster of Entities & Value Objects with a carefully crafted consistency boundary.

Rule: Model True Invariants in Consistency Boundaries

• An invariant is a business rule that must always be consistent.

• There are two types of consistency: transactional & eventual.

• An Aggregate is synonymous with transactional consistency.

Rule: Design Small Aggregates

• A large cluster limits performance & scalability

• Performance & scalability are nonfunctional requirements that cannot be ignored.