Local, first, forever

The post says local-first software keeps data on the user’s device but still needs internet sync for things like backing up and syncing across devices. That creates a risk: if the company disappears, the sync service may disappear too.

It proposes using common cloud file-sync tools such as Dropbox, iCloud Drive, OneDrive, Google Drive, or Syncthing as a simple sync layer. With CRDTs, conflicts can be merged automatically, and the article shows several layouts for doing that: one shared state file, one file per client, or append-only operation logs split into chunks.

Reading notes

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• Local-first software keeps data local, but still syncs online from time to time.
• Sync across a user’s own devices depends on some server-like component.
• If the company goes out of business, syncing can stop working.
• File-sync services are common and have multiple implementations.
• File sync is a simple protocol with little API surface.
• With a state-based CRDT, two conflicting state files can be opened, merged, and saved back.
• A file per client avoids Dropbox-level conflicts because each file is only edited on one machine.
• An operations-based CRDT can write operations into append-only files.
• Long operation logs can be split into batches to reduce sync work.
• The demo uses Automerge for text merging.
• The conclusion is that basic file-sync services can be enough for casual local-first sync.