In a production environment, at scale, this is a relatively uncomplex example, I think. At any rate I've seen significantly more complicated multi-service architectures for what would also have been called a "front-end" business.
Could you point me to more complex examples?
There's a very long discussion, somewhere, of Amazon's eventually-consistent architecture that I'd say is definitely on the high-complexity side of things. Unfortunately I can't find the link I'm thinking of, at the moment.
Of course, when you actually go to found the company, you should forget all that scalability nonsense and start with the simplest system possible. However, it's worth having an image in your head about how the system will evolve and what the appropriate response to various scalability challenges is.