You won’t need a lot of effort to scale even with a Go backend deployed on an EC2 instance in the majority of cases.

Serverless is cool when you start with 300 users and you’re still in the free tier plan. After that, it’s going to cost you a fortune when you really need to scale, and I’m not even thinking about the time that you would need to waste writing everything back to a monolith/microservice, because that is what’s going to happen most likely.