# ADR 0010: cr-sqlite DB Sync

## Status

Accepted.

## Decision

Database sync uses local SQLite databases with cr-sqlite-compatible
`crsql_changes` tables or views. Geth extracts typed change batches, exchanges
them over the protected Iroh control path, checks schema metadata before
application, and applies compatible batches through the local `crsql_changes`
interface.

The prototype does not add a second snapshot transport for DBs. CAS-backed DB
snapshots or change-batch blobs are deferred until the change path proves too
large for the control path or until initial peer catch-up needs snapshots.

## Consequences

The prototype has deterministic fixture coverage for extraction, application,
two-node Iroh exchange, authorization, schema mismatch detection, and live-sync
watermarks.

A real cr-sqlite extension integration test is intentionally not marked done in
this environment because there is no `sqlite3` CLI or cr-sqlite extension
artifact available to load. The blocker is environmental, not a protocol
decision. When the extension is available, add a two-node test that creates a
real cr-sqlite-enabled table, mutates one node, runs `geth db sync`, and proves
the second node applies the change through cr-sqlite.