I built a niche seasonal app on Bubble that gets a “big” (it’s all relative 
) traffic spike every March. This year in March the app had 126,000 pageviews, with numerous spikes of 1,000 pageviews per hour:
During peak moments in time, I might have 50-75 users on the site concurrently, but generally more like 20-30 concurrent users during peak hours. The app has some complex searches and workflows that are constantly triggered during those times.
The app generally runs on a monthly Personal plan, but on peak days I upgrade to Professional and add extra capacity. I think I added between 2 and 4 extra units on peak days this year and that was enough to keep capacity from spiking above 100%, which kept the app running smoothly. During non-peaks, I downgrade back to Personal. I agree that auto-scaling would be wonderful vs. having to predict/monitor your own peaks, upgrade manually, have Bubble charge you for a month at that new rate, and then get a credit for unused time upon downgrade (with an emphasis on the word credit — it’s not a refund, so beware this process if your app is on an annual plan).
It’s on you to optimize your app for performance, of course, but generally speaking Bubble can handle the kind of traffic you’re talking about.