Distributed consensus is a foundational abstraction of distributed systems. Long believed impossible to achieve, distributed consensus serves as a cornerstone for building reliable and scalable distributed systems. It allows a group of redundant processes to advance in lockstep to act as one so that at any time, some processes in the group can compensate for the failure of others.
Failing to reach consensus is often considered catastrophic for the application at hand. Did the transaction commit or abort? Did operation A happen before operation B? Was the lock acquired by component 1 or component 2? Any disagreement on these questions quickly results in incorrect behavior. Therefore, the consensus problem has garnered outsize interest in both the theoretical and practical realms of software engineering.