I'm new to server architecture and have been reading around a lot but have not yet had a solid opinion on if the setup below is good practice or not and was hoping someone with more experienced can give me confirmation if I'm setting up my architecture correctly:
I'm really concerned about the speed of my rest api as the regions offered in digital ocean seem significantly smaller in contrast to a cdn like cloudflare. How much does this matter when affecting my speed and is a service?
I know this might sound ridiculous but the region issue makes me wonder if hosting a rest api express server on a cdn would be better than a place like digital ocean. (my instincts tell me I should't do this on a cdn but am at a loss for reasons and hope someone can provide clear reasons why I can or shouldn't host an express rest api server there.)
From my knowledge I would do this a little differently.
A CDN is used to serve content hence the name CDN (Content Delivery Network). The CDN its self doesn't serve the content but it routes the user to a server which serves it. For example if you have a server in the US, France and Asia and you where from the UK and requested the website with images hosted on these servers. The CDN would direct you the the closest/best server for you. In this case that would be the server in France.
So to answer your question it isn't a bad idea to host the RESTful API on the CDN but you would need multiple servers around the world (if you are going for worldwide) and use Cloudflare CDN to direct your traffic.
This is what I would do: If your not expecting loads of traffic (like millions) just have 1-2 servers in each location so 1-2 in North America, South America, France (EU), Asia and maybe Australia. This will give you decent coverage. Then when you setup your CDN that should handle who goes where. Using node and nginx will help you a lot this will allow you to get cheaper not as powerful servers because they are pretty light weight.
Now for your databases you can do one of two things have one dedicated solution somewhere which will be as little latency for all regions somewhere like France (EU) so its more central or you can have multiple and have them sync. Having multiple databases which sync will be more work and will require quite a bit of research. Having the one server is a lot easier to manage.
The database will be your biggest problem deciding whether to do with one and deal with latency or multiple and have to manage them and keep them in sync. Keep in mind you could go with a cloud hosting platform to host your database this would help you with the issue because a lot of platforms will offer worldwide coverage as well as providing synchronised databases. You will however run into the cost issue when using cloud platforms.
Hope this answers your questions and provides you with the knowledge you need!