> Domino effect: one bug can take down the entire system at once

It bothers me that this is always set as a selling point for microservices, when it's actually the opposite. With monoliths (or at least monorepo) it's easier to test complex flows. When you split into microservices, they are still there, but there are so many boundaries in development that you end up testing in prod. For me it's a bit like unit tests vs integration tests. It means to naively think that all those unit tests somehow interact together to define the functionality that you want

From my experience, at least around 10% CPU util (I have seen upto 30%) goes towards JSON wrangling that is inherently a part of microservices. I understand that there are better options like rpc etc but all these will inevitably be worse pure function calls.

> but all these will inevitably be worse pure function calls.

It's the price to pay for loose coupling using an ubiquitous and widespread data interchange format that is extensively supported by a myriad of standard tools and, more importantly, is easy to read and debug.