quick question, if we're building a microservice based api using AWS + Lambda + API Gateway, would you recommend using a Pulumi Project per microservice?

I recommend having projects per deployment schedule. If 10 microservices are always deployed together, then they should all be in one project. If another microservice can be deployed at any time, without considering others, then it should be in its own project.

we do one

.pulumi

file with a project for each repository. Some will be stand alone repos, other will be mono repos. I guess an approach similar to what you would find in say Flux for gitops approaches is possible, but im a big fan of keeping things simple (at least at the beginning).