For a network engineer, HA of network functions is managed by FHRP or by routing protocols.
FHRP protocols rely usually on multicast to discover other members that will share a VIP (Virtual IP). The VIP will be used by hosts as a redundant next-hop.
But… there is no broadcast/multicast in the cloud, so no FHRP.
The AWS documentation shows an example about how to create a redundant NAT instance to serve two subnets.
I will not discuss the trade offs of the proposed solutions (using ICMP for health check, really?) only a consideration about the skills.
Linux and bash scripting are not optional skills for network engineers, even more when moving to the cloud.
The best time to learn Linux was ten years ago. The second best time is now!