This chapter covers the third of our little trio of topics: replication, scalability, and high availability. At the end of the day, high availability really means “less downtime.” Unfortunately, high availability is frequently conflated with related concepts such as redundancy, protection against data loss, and load balancing. We hope that the preceding two chapters have set the stage for a clear understanding of high availability. However, this chapter can’t be singularly focused; like the others in the trio, it must synthesize a few related topics.