A primer on how replication works including elections, and how replica sets are also shards. From there we will go into how sharding works from what meta data lives where, to how primaries hide data they do not “own” such as orphans. Next we will talk through some basic rules to keep in mind with sharding and give some ideas on how you start chasing a shard key. This is not a shard key deep dive as that would be a whole series of talks on its own however we will arm you with the tools to start your journey and understand the pros/cons of it.