Offline-first apps sound like the future: instant loading, privacy by default, and no more spinning loaders on flaky connections.
But in practice, very few apps get offline support right. Most simply queue changes locally and push them when the network comes back (spoiler: this doesn’t really work). Eventually, users see a scary banner saying “changes may not be saved.”
The reason is simple: syncing is hard.
When you build a local-first app, you’ve effectively created a distributed system. Multiple devices can mutate data independently, sometimes offline, and later must converge to the exact same state without losing data.
There are two main challenges to solve:
Unreliable ordering Conflicts
Let’s go through them.
1. Unreliable Ordering
In a distributed environment, events happen on multiple devices at different times. If you just apply them as they arrive, you get inconsistent results.
Example:
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