Eventual consistency of state is powered by distributed, lock-free consensus. Lock-free consensus is build on a basic principal: monotonic data structures. Monotonic data structures are high-level data structures that cannot be modified in conflicting ways – for example, an append-only set. By creating advanced monotonic data structures (config-free replicating data types, or CRDTs), and reframing problems in monotonic forms, we will show how eventual consistency works.