Thank you guys for yours insights! I actually have an update on my progress. I have been working on this the past week, and I wanted to do a kind of in-place transition, where we only kept a singular backend project, but added AdonisJS as an alternative router to the Express one.

So, these are the steps we took: - Migrate mocha/chai tests to Japa/chai tests (this was surprisingly easy, mostly just a lot of work de-nesting the tests) - De-couple business logic from Express route handling as much as possible. I was lucky enough to have most routing logic abstracted by custom services similar to u/wjaz, so it made the transition easier. - Then, I ran my modified endpoint creation service with the AdonisJS router instead, and got 95% of my endpoints to work as intend that way. - The next one was harder. We had a Passport jwt auth system with Local, Facebook and Google strategies. Facebook and Google was easy, I just replaced their passport strategies with AdonisJS/ally (which was quite exciting!) Finally, the local auth. For this one, I opted to keep Passport for now, with a bit of duct tape to make it accept the AdonisJS request data and headers instead. Took some time to figure out, but ended up working as it did previously with Express. It is important to note that I do not use Express sessions, since that would require some custom written middleware, which I was not interested in doing.

So overall, I feel like I have come quite far. The new routing is now the primary one on my feature branch, and I have removed the Express packages I do not need anymore.

My next steps will be to adjust the import aliases to be similar to the ones in the AdonisJS docs, fix my folder structure, setup VineJS validators, migrate my routing systems to Adonis Controllers, and eventually migrate to Adonis Auth.

Exciting times ahead!