tl;dr They can scale to hundreds of concurrent users without trouble, and likely to thousands or tens of thousands of concurrent users if designed appropriately and coordinated with the Bubble team. Plus, they have an incentive to support you at larger scale if / when you get there.
@supernaturally, I think Bubble can support a very large number of concurrent users. Afterall, they support all of our Bubble apps simultaneously on the same infrastructure. So, having a few hundred concurrent users on your site/app wouldn’t change the overall load much at all.
Additionally, the Bubble team now offers plans that enable you to put your app on it’s own server to enable more control and customization of the hardware, etc.
All of this being said, scaleability also depends on what you’re having people do with your app. If you’re doing an AirBnB clone, for example, then showing 10 listings at a time is standard. If you, instead, wanted to load 1,000 listings every time the user loads the page, then the performance is going to be much worse for that user and each of your users may eat up 100x more bandwidth than the typical user of another site. Additionally, if you’re doing lots of searches, filters, sorting, etc. then it can slow down the performance considerably.
Big companies spend lots of time to optimize the queries once they’re large. Bubble gives us a lot of flexibility in deciding what we load to the page, whether we load it on page load or after the full page has loaded, etc. So, I suspect we can get pretty far with this.
Bubble’s sweet spot has historically been early stage companies who are looking to build something quickly and quickly adapt to customer needs, and they are now maturing beyond that and are focusing on strengthening the related capabilities. They can definitely scale to a fair extent, and if you’re a huge success I’m sure the Bubble team will do what they can to enable your continued success because your success helps them. And, they’ve aligned their interests with yours/ours by keeping prices low for apps without much traffic, so they definitely have a financial incentive to keep successful apps on their platform.