A Map of Sync

In the words of a recent tweet from Rocicorp’s Aaron Boodman, “[the local-first/sync space] is a big, beautiful, hot mess.” Between the local-first movement, a bounty of new database startups, academic research like CRDTs, and internal app frameworks powering products like Linear, it’s hard to know what’s going on and how everything relates to each other.

A few of us at Convex have worked for over a decade on sync at Dropbox, and we've been working the past few months on extending Convex's sync engine for better offline support and responsiveness. Here are our notes for how we've been keeping things straight.

In this document, we’ll present a taxonomy for sync that organizes a few sync platforms across nine different dimensions1 and then walk through the dimensions one at a time.

In any system, it’s often fruitful to start with nouns over verbs, and in this category, we’ll start by dissecting a sync app’s data model. What data flows through the system, and how does it change?

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