AWS is a great place to start if you're not yet sure what resources and scale you need. You can play with various solutions and easily scale up.
It makes developing so much more efficient when you don't have to make major choices up front, and can buy yourself some breathing room by throwing temporary resources at most performance issues while you review your architecture.
That either stabilizes to a point where you have an architecture that you can implement cheaper and more efficient using more traditional hosting solutions, or you come to a point where you really need AWS's flexibility.
One caveat though: don't make your architecture too dependent on AWS-specific services until you are 100% AWS is the right choice for the long term.
It makes developing so much more efficient when you don't have to make major choices up front, and can buy yourself some breathing room by throwing temporary resources at most performance issues while you review your architecture.
That either stabilizes to a point where you have an architecture that you can implement cheaper and more efficient using more traditional hosting solutions, or you come to a point where you really need AWS's flexibility.
One caveat though: don't make your architecture too dependent on AWS-specific services until you are 100% AWS is the right choice for the long term.