Discussion on: How do you protect your backend API in your microservice if you use a Single Page Application on the frontend?

[Usama Ashraf]

Largely subjective. You might even try developing your own gateway, nothing wrong with that.

I'd prefer using load-balancing, rate-limiting features if they ship with the gateway. Though consider caching as well.
Else, an Nginx/HAProxy instance could be placed in front of multiple instances of the gateway. Best of luck!