The second problem is the amount of network interactions added to build the same application. In the monolithic version, even if the code gets messy, everything happens in the same process, and you can send back the result without having to call too many backend services to build the actual response.

That requires extra attention on how each backend service is called, and raises a lot of questions like the following:

• What happens when the Booking UI cannot reach the PDF reporting service because of a network split or a laggy service?
• Does the Booking UI call the other services synchronously or asynchronously?
• How will that impact the response time?

We will need to have a solid strategy to be able to answer all those questions, and we will address those in Chapter 5, Interacting with Other Services.