ddd4j Data

Overview

Pick the persistence model first, then the technology. Snapshot Repository, Event Sourcing, Projection, and Outbox are distinct responsibilities that may be combined but must not blur transaction boundaries.

When to Use

• Choosing the persistence technology: JDBC, JDBI, JPA, MyBatis/MyBatis-Plus, R2DBC, Panache, or ESDB EventStore.
• Mapping between AggregateRoot and PO/Entity classes, and wiring Query<M> persistence scopes.
• Implementing the EventStore / AsyncEventStore port with expected-version checks and atomic batch appends.
• Building read models with ProjectionRunner / ProjectionService and ProjectionPositionRepository.
• Implementing the Transactional Outbox with claim / send / confirm semantics.
• Defining transaction boundaries, tenant scoping, encrypted fields, and auditing at the persistence layer.

When NOT to Use

Do not use this skill when: