Paxos is a protocol for solving consensus through state machine replication in an asynchronous environment with unreliable processes. It can tolerate up to F concurrent replica failures with 2F+1 total replicas. This consensus protocol is then extended with a stable leader optimization to a replication protocol (commonly referred to as Multi-Paxos) to assign global, persistent, total order to a sequence of client updates. The protocol works by having multiple replicas work in parallel to maintain the same state. This state is updated on each request from a client by each replica, allowing it to be automatically replicated and preserved even in the case of failures. The basic algorithm was famously described by Leslie Lamport in his 1998 paper, The Part-Time Parliament. It was later clarified in his follow-up paper from 2001, Paxos Made Simple. It does so by breaking the global command slot space into subspaces, each owned by a single replica. Replicas then attach ordering constraints to each command while voting on them to allow for proper ordering during command execution. For more intuition on how this works, check out the presentation given at SOSP '13, and for a full technical report and proof of correctness of the protocol, check out A Proof of Correctness for Egalitarian Paxos.