Prime Video Switched from Serverless to EC2 and ECS to Save Costs

Prime Video Switched from Serverless to EC2 and ECS to Save Costs - InfoQ
В статье не указывается конкретно что привело к такому решению, только упоминается о том, что были обнаружены бутылочные горлышки в работе системы

Amazon Prime Video reduced cost by 90% by switching from microservices to monolith : r/sysadmin
на reddit дан хороший комментарий на тему необдуманного перехода на микросервисы/serverless:

Microservices have overhead. What used to be a simple inter-process communication or even an in-memory call between two small parts of a system becomes a full HTTPS, OAuth, JSON encoding/decoding exercise every time one of those short conversations needs to happen. When your system is blown apart into 500,000 pieces and each communication requires that setup, AND you're being billed for each transaction, the cost and complexity adds up.

The reaction against monoliths was the need to replace the entire application in one shot, meaning developers would actually need to test stuff. DevOps means there's no more testing and we fail forward in production, and the only way you can do that is by having tiny functional pieces so you can find/fix stuff fast. I don't think there's anything wrong with saying these super-chatty parts of the application belong together without the need to open millions of connections all the time.