In this chapter, we discussed replica sets and how to administer them. Starting from an architectural overview of replica sets and replica set internals around elections, we took a deep dive into setting up and configuring a replica set.

We learned how to perform various administration tasks with replica sets and the main options when we want to outsource operations to a cloud DBaaS provider.

Finally, we identified some of the limitations that replica sets in MongoDB currently have. In the next chapter, we will move on to one of the most interesting concepts in MongoDB, the one that makes it achieve horizontal scaling, sharding.