Not a startup...but I do know of (I am consulting for them on the project) an established SaaS company that is impressively large and successful in their vertic

Not a startup...but I do know of (I am consulting for them on the project) an established SaaS company that is impressively large and successful in their vertical that is porting from PHP/Postgres to ASP.net core and running it all on Azure Biggest pain so far is the versioning FUD around .Net core, standard etc. That said, it is not really an issue. From a risk mitigation perspective we are trying to lean on some other established and long tested things like Dapper as a micro-orm and staying away from fluid elements that we really want to use like SignalR until they settle down some. We also went as green field as we could, no attempt to port code in the classic sense, ground up rewrite.