Introduction

Picture two doctors updating the same patient record at the same time - one in São Paulo, the other in London. Both are offline. When connectivity returns, whose changes prevail?

This is not a hypothetical. It is the everyday reality of distributed systems: multiple nodes, no shared clock, no guaranteed network. The conventional answer has long been locking - one node waits while another writes. But locks are fundamentally incompatible with availability. When the network is unreliable, waiting is not an option.

Conflict-free Replicated Data Types (CRDTs) offer a different path: let both doctors write freely, and design the data structure so that merging their changes is always mathematically sound - no coordination required, no central authority consulted.

What Are CRDTs?

A CRDT is a data structure purpose-built for replicated, eventually consistent distributed systems.…