CRDTs
Data structures that merge concurrent edits automatically — how offline-first health apps sync without a referee.
In one line
A CRDT (Conflict-free Replicated Data Type) is a data structure designed so replicas edited independently — offline, concurrently — always merge to the same state, by mathematics rather than by a central server deciding winners.
How it works
Operations are designed to be commutative: apply them in any order and arrive at the same result. Counters, sets, maps and rich-text sequences all have CRDT formulations; libraries like Automerge and Yjs package them for application use. The cost is metadata (tombstones, per-item clocks) and the discipline that merging without conflict is not the same as merging with clinical sense — a deliberate review step can still be the right design even when the math can auto-merge.
Where it shows up in digital health
Community-health-worker apps that work offline for days (the offline-first pattern in LMIC deployments), collaborative care-plan editing, and sync layers of PWAs — including the offline reading this platform plans. CRDTs are why "last write wins" is no longer the only answer to a nurse and a doctor editing the same note in a connectivity gap.