I have a Node.js REST API which is expected to serve a total of approx 3000 requests(inbound+outbound) per day, in production. Which EC2 instance type would be the most appropriate choice for this kind of an app? I'm confused between t2.small and t2.medium and how many should I setup into the load balancer?
In your case t3.nano can also be enough as the number of requests are very low. Regarding how many, I would always have minimum 2 instances against load balancer in different avaialbility zones. e.g if you are using eu-west-1 region then 1 box can go in eu-west-1a and second in eu-west-1b.