Very interesting and exciting! I have heard of others that have taken this approach with great success. As @winston mentioned, Shiny is perfectly capable of scaling to any magnitude you need. Obviously, there are best practices to learn about building multi-tenant applications along the way, but there are many of us who are happy to help there and plenty of resources to facilitate such learning!
Some of the big factors you will need to consider if you're looking to build on top of Shiny:
- What kind of user authentication are you shooting for? How do you plan to manage user accounts?
- How many resources for performance does a single R process / instance of the app need? How many concurrent "Shiny sessions" / users can a single R process support?
- Do you have the expertise to configure linux virtual machines? Do you need dedicated infrastructure?
You don't need to answer all of these questions up front, and your answers may change over time. Obviously, the open source counterparts to RStudio's Pro Products (Shiny Server / RStudio Server) are welcome to be used - however, you would need to build the authentication yourself and will need to do much of the work around scaling your application.
If you're looking for a boxed way to host and scale your Shiny applications, the easiest way to get started (and maybe a good place to start your proof of concept) is shinyapps.io . This requires zero devops knowledge, since servers are maintained for you in the background. You also get user authentication (on the paid tiers) and the ability to easily scale your application to serve additional users if needed.
Shiny Server Pro / RStudio Connect will require a bit more experience with linux, since you have to set up the server yourself (on AWS, GCP, wherever). You get several kinds of authentication built in and can scale your Shiny application pretty naturally. These are software products built expressly for using Shiny in the enterprise / commercial space, and handles much of the "hard stuff" for you. Support comes with that contract - so if you get stuck, you've got access to help, too. There is also a Small Business discount and a free 45-day eval of all of our pro products, if you're trying to determine your price point, what is feasible, etc.
If you like the idea of a pro product, but don't have the linux expertise necessary, I know there are some consultants / organizations that will set it up for you, etc.
I'm sure there are other options out there, so definitely check those out! If it's a good fit, one of the big pluses of using one of RStudio's pro products is that you're ultimately funding the open source development of Shiny, the tidyverse, the IDE, etc. Our pro customers make our open source software possible!