Come to this session to learn about the internal workings of MongoDB replication and replica sets. We will track the lifetime of a replicated write: from the moment it enters the primary server, as it travels out to secondary servers, and finally as it is reflected back to the primary (in case the write has an associated write concern). In particular, we will discuss the techniques MongoDB uses to ensure correct write ordering on secondaries while still keeping up with the primary and servicing client reads as well. This is an advanced session intended for those who possess a basic understanding of MongoDB and general programming concepts.