I'm working a lot with a Bubble/Node/Express stack these days, here's why:
Bubble is super fast to build front end pages, comes with the database, and most of the workflows are perfect for user functionality, payments, and most "out of the box" software app functionality.
But when actually building some complex functionality, which requires heavily leaning on APIs and transforming data, that quickness is lost. I think this is where a ton of people get stuck in Bubble and either 1) settle for an app that doesn't do that much or 2) take months to master the no code skills that could have actually been done faster with some light code.
Enter Node/Express - with a few terminal lines, you've got your own API up and running, and with Bubble's API connector you can pretty seamlessly connect it to your Bubble app. You can take advantage of turning those API routes into a cron job in Heroku, which is way easier than handling scheduled workflow runs in Bubble (plus it's free, Bubble makes you pay quite a bit for them).
If you want to dive in more, I made a video walking through how I used this stack in an app I built: https://youtu.be/dVGbrLF7sEo
Anyone else using Bubble/Node/Express?