  Internet-scale distributed systems often replicate data at multiple
geographic locations to provide low latency and high availability, despite node
and network failures. Geo-replicated systems that adopt a weak consistency
model allow replicas to temporarily diverge, requiring a mechanism for merging
concurrent updates into a common state. Conflict-free Replicated Data Types
(CRDT) provide a principled approach to address this problem. This document
presents an overview of Conflict-free Replicated Data Types research and
practice, organizing the presentation in the aspects relevant for the
application developer, the system developer and the CRDT developer.
