juniorDDD
What is a Service in DDD?
Updated Apr 28, 2026
Short answer
When an operation doesn't naturally belong to an Entity or Value Object, it is implemented as a standalone Service.
Deep explanation
DDD is not just about coding; it's about modeling the business. By using Ubiquitous Language, we ensure the code reflects the mental model of the domain experts. Entities handle identity (like a User ID), while Value Objects handle data (like an Address).
Real-world example
An e-commerce system where 'Order' is an Entity, but 'Shipping Address' is a Value Object.
Common mistakes
- Making everything an Entity even if it doesn't need identity.
Follow-up questions
- Why are Value Objects immutable?