There are definitely more performant options. I considered ZeroMQ for a while, and almost decided on it, but went for HTTP/REST because of the built-in error handling, and request-response style (as far as I can see, I would have to implement all of this if I chose to use ZeroMQ).
I also chose HTTP because, at the end of the day, I still get almost ~1000 payment per second after the change (on a laptop). VISA handles 200k payments/second at peak, so that's peak VISA levels on 200 MacBook Pros.
I see I might have misspoke when I said "front-end". It's really the front-end (logic part) of the backend server, which now comprises two parts: stateless logic ("front-end") and database (stateful) backend. So I haven't considered Websockets.
I also chose HTTP because, at the end of the day, I still get almost ~1000 payment per second after the change (on a laptop). VISA handles 200k payments/second at peak, so that's peak VISA levels on 200 MacBook Pros.
I see I might have misspoke when I said "front-end". It's really the front-end (logic part) of the backend server, which now comprises two parts: stateless logic ("front-end") and database (stateful) backend. So I haven't considered Websockets.