## Services
Services are where business logic lives.
The service layer speaks the specific domain language of the software, can access the database & other resources & can interact with other parts of your system.
Here's a very simple diagram, positioning the service layer in our Django apps:
A service can be:
- A simple function.
- A class.
- An entire module.
- Whatever makes sense in your case.
In most cases, a service can be simple function that:
- Lives in `<your_app>/services.py` module.
- Takes keyword-only arguments, unless it requires no or one argument.
- Is type-annotated (even if you are not using [`mypy`](https://github.com/python/mypy) at the moment).
- Interacts with the database, other resources & other parts of your system.
- Does business logic - from simple model creation to complex cross-cutting concerns, to calling external services & tasks.