three-layer-fp
realworld layer
Everything that one need to talk to but it's awful and it has nothing to do with logic of application.
Examples:
- Object storage like S3
- Database like Postgres
- HTTP calls
- Other stores like Redis
- Logging facilities
- Metrics infrastructure
- Payment processor like PayPal
domain layer
Everything that achieves some effect by altering or reading the outside world but in context of our domain
Examples:
- You need list of clients from some store. Underlying database is hidden you only have functions like
def getClient(clientId:Id): F[Client]- You need to store your ML algo to S3 store. S3 store is hidden you only see a function like:
def storeModel(model:MLModel): F[Unit]Sequencing happens based on F having a Monad instance.
businesslogic
Pure logic of how we want to orchiestrate out application. There should be no effectful function here.
One can use types like Option and Either but not IO, Future. All values that needs to be read from the outside
world shoule alreadu be obtained in the lower level layers.