ddd-domain-service

One-line summary

A domain service is a stateless operation in the domain layer that doesn't naturally sit on a single entity or value object — usually because it coordinates multiple aggregates or involves a domain computation that isn't anchored to one thing.

When to use this skill

• A cohesive domain operation involves multiple aggregates (e.g., transferring money between two Account aggregates).
• A calculation involves domain types but isn't naturally a method on any of them (e.g., currency conversion, given exchange rates).
• Forcing the behavior onto one of the participating entities would make that entity "know too much" about the others.

When NOT to use this skill

• The logic fits cleanly on a single entity — put it there.
• The work is application-layer orchestration (handling a use case, opening a transaction, calling repositories) — that is an application service, not a domain service.
• The work is infrastructure (HTTP calls, database access, message sending) — that is an infrastructure service.

Core content

Three kinds of services often coexist in a DDD codebase. Keep them distinct: