Q:

Express-rate-limit vs NGINX in a node server

I'm currently using express-rate-limit module to block multiple requests from the same ip or logged in user account in my node server, and this is working pretty good against DoS attacks. This server is a small local business that requires only one instance, as it doesn't have too many users and it's computing requirements aren't too intensive.
I've been reading a lot about nginx lately, and many people recommends using it in node servers, but I can't see the major advantages of using it in this kind of application.
How would nginx be better for my application? What can it do that other npm modules can't in terms of security for a single server application?

A:

Well I am not an NGINX expert but I use NGINX in production currently on my EC2 instance. When it comes to rate limiting there are a couple of options available with respect to express

You can use redis as a store, get the IP address of each incoming request and check how many hits they currently have before deciding to service them. This could be a middleware that works on all routes
You could use a library like express-rate-limit or rate-limiter-flexible which will handle the redis part for you
Now when you take NGINX, it is a web server whose strongest point is not rate limiting to be precise. It still supports rate limiting though if you modify the configuration. HERE is an insight into NGINX rate limiting.
Another option you havent considered is called HAProxy which is a load balancer which is considered superior for tasks such as rate limiting. You can read about HERE

Lets talk about the second part of your question

Rate limiting inside an application is a bad idea. It does not belong to the application as such. It is not a part of business logic. Also, It does not work well with clustered mode (more than one cores running express at the same time) unless you tweak it for supporting cluster.
Rate limiting using NGINX configuration just needs 2 extra lines as shown in the earlier link I posted. If suddenly you want to add an extra route or exempt some route from rate limiting NGINX can easily do that. 
If you want to exempt your cloudfront addresses or CDN server addresses from being rate limited, you can add a whitelist of IPs to NGINX conf so that it will exempt them. Doing this in the application will be a real pain as you would have to git commit, redeploy etc. THIS answer covers how to exempt addresses

