[iamsomewalrus]

In general, it's not uncommon for startups of the Goodreads vintage to outgrow a simple Rails app and use a more service oriented architecture. We've actually had services for about 5 years now, but we haven't been very vocal about it.

As I mentioned in another comment I, personally, wouldn't advocate for new teams or startups to use a service oriented architecture right out the gate. It's too easy to end up with a distributed monolith (circular dependencies between services, services uptimes that are tightly coupled). Engineers also tend to underestimate the build tooling, observability excellence and discipline you need to make it seamless.