⚡️ Offline-first and real-time sync are essentially the same problem
The shared foundation of offline support and real-time synchronization in local-first applications.
Offline support and real-time synchronization are often treated as two separate features. But look under the hood of local-first architecture, and it turns out that they rest on exactly the same foundation:
- Client-side ID generation, so newly created records do not have to wait for a backend response.
- Optimistic updates: the interface responds instantly.
- Conflict resolution when data changes in parallel.
- A background data-exchange mechanism to reconcile changes on the client and server.
If a library or architecture gets offline support right, real-time support comes almost for free (and vice versa).
In the article, the author draws on experience with Verdant, TanStack DB and Zero to explore these concepts, storage approaches and pitfalls in detail.
Recommended reading for anyone interested in the architecture of local-first and real-time web applications.