It's a restful api that doesn't hold any state, we use jwt (jsonwebtoken) for auth. It's essentially a collection of routers for different actions. Mostly crud, with few exceptions like webhooks, auth flow. We often use middlewares e.g. for things like validation. Everything is written in ts/tsx so the client/server do share types. We serialize data to use it in a standarized/known format in the UI.
If you like the middleware system in express you might be interested in starfx, which implements the same middleware but for fetching and data synchronization in the FE. It has a simple but powerful state management system and leverages structured concurrency to manage side effects.
