If the question "are there any case studies where microservices went well" is a valid question, then so must be, "are there any case studies where monolithic architecture went well".

My point being that if and only if we have a track record as an entire field of making decisions based on case studies, AND if case studies have a track record of being objective rather than proffered as a result of a marketing agenda, then the question is ultimately legitimate.

There are more shops by total count that fail with monolithic architecture. That's inevitable just based on the infinitesimal number of projects executed as service architectures rather than monoliths at large in the wild. But still, we carry on with monolithic architectural style as if its outcomes were assured.

It's far easier for the vast majority of developers to build a monolith because it allows development to proceed without having to have any knowledge of or practice with the tricks and traps of distributed systems - an entire body of knowledge that a developer might never get meaningful and practical exposure to for an entire career.

The trouble starts when microservices are attempted by developers who can't imagine that there are entire bodies of software development knowledge that developers aren't presently in possession of.

Microservices is just, as Adrian Cockroft used to say, "Service-Oriented Architecture with bounded contexts".

Web development is absolutely not a preparatory course in service oriented architecture. But the vast majority of web developers who attempt to take on SOA while simultaneously presuming an omniscience in all things software development due to their experiences only with monolithic web development will often fail to build a SOA. They usually end up with something that isn't quite SOA and isn't quite a monolith. And that's where the failures largely come from.

I work exclusively in microservices and SOA, and have since 2015. Before that, I worked principally as a web app developer, and did some work off-and-on in SOA implementations. And before that I spent years becoming oriented to the architecture. I don't make the mistakes that web developers typically do when they presume that web development knowledge is a sufficient prerequisite for working in SOA.

So, it's not a question of whether an architectural style works or doesn't. The majority of failures in microservices can be attributed to ignorance and to the narcissism that is permissive of it.

So, I would ask this question instead: Are there any cases where developer over-confidence and over-simplification went well?

These qualities don't tend to serve any architectural style well.

I've never heard of a well-designed SOA not going well. Every single case of microservice project remediation that I've participated in had as the most significant contributing factor an utter disregard for the body of knowledge that the microservices architectural style is built upon.

There are a lot of things that developers can get away with when doing the kinds of tinkering and wandering that typifies typical web development work. But those things don't work once we cross the line into SOA. And unfortunately, the incessant chasing after trivial resumé candy hasn't prepared the average developer for the rigorous mindset needed for SOA work.

As "microservices" became to next fad for perennial fad chasers of the software development world, they finally encountered a kind of work that they could not get away with by faking it. And so, we see a lot of failures. But the vast majority of the failures are personal failures and character failures, rather than failures of an architectural style.

The fat part of the developer bell curve was simply overreaching when it presumed to try to get away with building service architectures with the same level of disinterest in architecture and process that we can get away with in typical web development. Like a kid with copious experience building kites presuming to strap themselves to a hang glider and just "going for it". The outcomes are mostly predictable.

In the end, if a little time is invested in learning the fundamentals that have so far been eschewed for the sake of expediency, anyone can succeed with SOA and microservices. It's not that the realities of the architectural style are unlearnable, but it can't be arrived at by the level of tinkering and wandering that we can just get away with in monolithic web development.