May I ask what high availability has to do with the microservices? Since many of my servers were designed for relatively large companies (like TELCO) high availability/reliability requirements were always there. Running 2 or more monoliths in parallel with the appropriate logic built in does not make them into micro services
if they are large enough and have components that need to scale independently than a bottleneck in one of those components may affect availability of the service.
Or may not. I design and create products that serve particular problem for customers while satisfying reasonable constraints. If it comes to a situation you've described than it will be spun into a separate component. I already told that I did and know how to do distributed applications. The keywords here are "WHEN NEEDED". And on modern hardware it is not in my cases.
also running two very large pieces of complex software in parallel is not always easy without breaking out the things that cant always be run in parallel :)
Whatever problems you MIGHT have with the monolith - the same problems will hunt you in your microservice implementation. You'll just have a lot more microservice related problems as an extra toppings. Also it sounds like you're bringing straw arguments without having practical experience
