Ditch Electron: Building a Local-First Sync Engine with Turso & SQLModel

Part 4 of the ERTH Architecture Series: Implementing offline-first database schemas, UUIDv7 indexing, and cloud-edge SQLite replication.

, we established a Zero-Trust shield around our Python backend (Robyn) using in-memory Opaque Tokens.

Our application is responsive, self-healing, and secure. But it is still stateless. If the user closes the application, all data disappears.

To turn our assistant into a true personal database, we need persistence. But we don't want a heavy database engine like PostgreSQL running on the user's laptop, nor do we want a simple offline SQLite file that isolates data on a single machine.

We want a Local-First Sync Engine:

1. 
   0.1ms latency: All reads and writes must happen instantly on local disk.


2. 
   Offline-first: The app must work fully on an airplane or subway without internet.


3. 
   Seamless Cloud Sync: When network is restored, data must replicate bidirectionally to the cloud.


4. 
   Multi-device roaming: Sync across laptops, tablets, and phones without data conflicts.

In this fourth post, we will build this layer using Turso (libSQL) and SQLModel, leveraging UUIDv7 and Tombstone deletion patterns to handle offline concurrency.

The Synchronization Architecture

Our Local-First database architecture relies on Turso's embedded replica synchronization:

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👉 Explore the open-source code on GitHub

Stay tuned for Part 5!