Ask HN: Best way to structure/architect an API with ExpressJS/TypeScript?

I've got major maintainability problems with my kind of amateurish webapp. I spent a bit of time the other day writing a bunch code that I just found out I had already written awhile back. I see a bunch of guides on Google but it's hard to judge how good they are without references/reviews. Are there some in depth guides on separation of concerns, service-oriented architecture, MVC, file structure, etc using Express? Or perhaps a really good reference project or two?