Conflict-Free Replicated Data Types

CRDTs enable distributed collaboration without central coordination. Used in collaborative docs, distributed databases.

Implementation

class GCounter:
    """Grow-only counter CRDT"""
    def __init__(self, node_id):
        self.counts = {}  # {node_id: count}
        self.node_id = node_id

    def increment(self):
        self.counts[self.node_id] = self.counts.get(self.node_id, 0) + 1

    def merge(self, other):
        for node, count in other.counts.items():
            self.counts[node] = max(self.counts.get(node, 0), count)

    def value(self):
        return sum(self.counts.values())

Use cases: Google Docs, Redis, Riak