If you've worked with a relational database in production, it's likely you have experience with replication. Relational databases typically provide master-follower replication, in which all data is written to a single master instance; then, behind the scenes, the writes are replicated to follower instances. The application can read data from any of the followers.
Note that master-follower databases are not distributed: every machine has a full copy of the dataset. Master-follower replication is great for scaling up the processing power available for handling read requests, but does nothing to accommodate arbitrarily large datasets. Master-follower replication also provides some resilience against machine failure: in ...
