In this chapter, we discussed the principles of building monolithic applications oriented to be split as microservices, depending on the business needs. As you have learned, the Atomicity, Consistency, Isolation, Durability (ACID) design principles are concepts that we need to have in mind in order to build high quality software.

You have also learned that we cannot assume that we are going to be able to design a system from scratch, so we need to be smart about how we build the new parts of the system and how we refactor the existing ones so that we achieve the level of flexibility required to satisfy the business needs and be resilient.

We also have given a small introduction about monolithic designed databases and how they are the biggest pain points when splitting a monolithic software into microservices, as it is usually required to shut down the system for a few hours in order to split the data into local databases. This subject could well be an entire book as new trends with NoSQL databases are changing the game of data storage.

Finally, we discussed how to align the teams of engineers in our company in order to be efficient while keeping the flexibility and resilience needed to be able to be agile, as well as how the Conway's Law impacts the conversion of monolithic systems into microservices-oriented architectures.

In the next chapter, we will apply all the principles discussed in the first three chapters, as well as a big dose of common sense to build a full working system based on microservices.