ts-ddd-simplifylisted

# Simplify — TypeScript DDD > Three similar lines is better than a premature abstraction. Abstract only when a pattern has appeared in at least three real cases. ## What to look for **Domain over-engineering** - VO wrapping a single `string` with no validation or behavior — remove it (keep if it enforces format like `Email`, `Money`) - Aggregate that only delegates to a domain service for every operation — collapse the service into the aggregate - Deeply nested event hierarchy (`DomainEvent → OrderEvent → OrderCancelledEvent`) — flatten unless used for polymorphic handling **Application over-engineering** - Handler with one line `return this.repo.findById(id)` — skip the use case, call the repo from the query handler directly - Command DTO with fields identical to the domain constructor params — collapse into one - Interface with a single implementation that is never mocked in tests — inject the concrete class; add the interface when a second impl is needed **Infrastructure over-engineering** - Mapper that copies fields one-for-one with no type conversion — consider if domain and ORM models are actually the same thing at this stage - Repository wrapping ORM with one-liner methods and no mapping or error handling — the layer adds no value yet ## Premature patterns | Pattern | Worth it when | Premature when | |---------|---------------|----------------| | CQRS with separate read models | Queries are complex joins or aggregations | Simple CRUD reads | | Event sourcing | F