In this chapter, we discussed replica sets and how to administer them. Starting with an architectural overview of replica sets and replica set internals involving elections, we dove into setting up and configuring a replica set.

You learned how to perform various administrative tasks with replica sets, and you learned about the main options for outsourcing 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 (which helps it to achieve horizontal scaling): sharding.