Invoking the Application Service / Use Case

In Domain-Driven Design, Application Services have a specific purpose.

The purpose of an Application Services is to get all the stuff needed in order for domain layer concerns to interact, than to save the result to persistence.

In the following example, using Interface Adapters (like IUserRepo), the responsibility is to:

  • Fetch the Aggregate(s) and any other objects needed in order to execute the domain logic.
  • Pass the objects to either an Aggregate's method OR a Domain Service.
  • Save the results of the transaction to persistence.

Howdy 👋

This is an online wiki and book about the basics of software design and architecture with TypeScript by Khalil Stemmler, Developer Advocate @ Apollo GraphQL .

This book’s mission is to teach developers the essential skills and practices to write testable, flexible, and maintainable code.

You can read more about the learning journey in the "Software Design and Architecture Roadmap 🖼️".

Already bought it?

If you’ve already purchased the book, click here to re-send your link. You can read the online wiki or download a copy of the book in PDF, EPUB, and Kindle versions.

Want access?

You can read the intro to the book for free and visit to buy the book/wiki (it's currently on pre-sale for 33% off)! For recent updates, click here. To get an idea of my writing, read some of my best free content here and here.

Need help?

Something not working? Have a question? You can reach me on Twitter or