Options to harden node server against ddos and other attacks

Hi,
I'm in the process of choosing a cloud service (running Ubuntu vps). Most likely it will be Digital Ocean or AWS ec2.
The server us to run node.js and optionally nginX. I'm looking at how to secure it against attacks from malicious users / bots.
There are several Front Ends that connect via an API to the node server and these run on different domains (enabled CORS on the server).

I know of Cloudflare and on a recent test, it blocked header infomation from the front-ends and I could not...

Options to harden node server against ddos and other attacks WordPress ...