I don’t get it : in the microservice approach, you can have services communicating with each others using event sourcing, but why forcing every service to work with event sourcing internaly ? Any requring transactionnal behavior, or at least transactionnal functions, could rely on a relationnal database to ensure atomicity.

The purpose of microservices seems to me to be able to have different internal architectures for each service. So why getting back a shoving a single one everywhere ?