Splitting the monolith

In the previous section, we discovered how to structure our application using Fastify plugins, separating our code into services and routes. Now, we are moving our application to the next step: we are going to split it into multiple microservices.

Our sample application has three core files: our routes for v1 and v2, plus one external service to load our posts. Given the similarity between v1 and v2 and our service, we will merge the service with v2, building the “old” v1 on top of it.

We are going to split the monolith across the boundaries of these three components: we will create a “v2” microservice, a “v1” microservice, and a “gateway” to coordinate them.

Creating our v2 service

Usually, the simplest way to extract a microservice is to copy the code of the monolith and remove the parts that are not required. Therefore, we first structure our v2 service based on the monolith, reusing the routes...