I'm not familiar with their products but it seems they had a four hour incident a few months ago:

https://status.yugabyte.cloud/history

You should not run a payment gateway on an inexperienced team. Start with something with lesser risk and then introduce the team to things like load balancers, keepalived, clustering and so on over time.

An hour of downtime is a lot once HA is something to invest in, and the first thing you need to do when there's an incident is to tell your customers what you're doing about it and the second thing they want to know is whether it will happen again. Since I don't know how Yugabyte works I'm not sure about the degree of lock-in, but preferably you should have an incident process where you at minute ten or so of downtime boot load balancing with a customer facing message at another infra provider and update DNS records, then start to rebuild the system there in parallel with the main incident response.