I'm always going to say that if you have third-party integrations where you call out to other organizations' services, that will be the thing that breaks down t

I'm always going to say that if you have third-party integrations where you call out to other organizations' services, that will be the thing that breaks down the most. You have to armor the heck out of it and plan for contingencies, and yes, that includes when third party is <Famous Company Where Surely Nothing Ever Goes Wrong>. Microservices are just a slightly more reliable version of that, since you can hassle the author as coworker instead of via harried FCWSNEGW support mouse.