It can take a long time to get a full-stack React & Node.js app up off the ground. But with the addition of API Routes, Next.js can do that in just minutes.
While circular dependencies may not directly result in bugs, they will almost always have unintended consequences. There are node packages that look for circular dependencies, but
It's possible to extend the default Heroku 30 second timeout by sending meaningless bytes back to the client. This post shows how to do so using Node.js / Express middleware.