There is a fundamental rule with distributed databases: you can pick any two of: * Maintaining data Consistency across the entire network * Maintaining data Availability across the entire network * Being able to deal with a Partitioning of the network into two or more disconnected pieces but you can never have all three. An example of this is the outage at GitHub earlier this month <https://www.theregister.co.uk/2018/10/31/github_lost_a_network_link_for_43_seconds_went_titsup_for_a_day/>. A link broke between the east-coast and west-coast halves of their network, and in an effort to maintain ongoing service availability on both sides of the partition, they ended up sacrificing consistency of the data. Which came back to bite them when the link was re-established, and the inconsistency could not easily be resolved.