Offline Sync Patterns

Provisional Numbering

Official document numbers (invoices, receipts) must be sequential and gap-free. Offline devices can't reserve numbers from Origin.

Pattern:

Create documents with provisional ULID-based identifiers (DRAFT-01JXQ3...)
Sync to Origin via CRDT
Origin assigns official sequential number via nextval('invoice_seq')
Official number syncs back to device

-- Device (offline)
INSERT INTO invoices (invoice_number, customer_id, amount, status)
VALUES ('DRAFT-01JXQ3...', 'cust-005', 750.00, 'draft');

-- Origin (on sync) — trigger assigns official number
-- Invoice becomes INV-26-04-00024

State Machine Transitions

ALTER COLLECTION invoices ADD CONSTRAINT invoice_flow
    ON COLUMN status TRANSITIONS (
        'draft'     -> 'submitted',
        'submitted' -> 'approved' BY ROLE 'manager',
        'approved'  -> 'issued'   BY ROLE 'accountant',
        'issued'    -> 'voided'   BY ROLE 'controller'
    );

Devices can create drafts and submit them. Approval requires manager role — only available on Origin.

Tax Rate Sync

Sync relevant jurisdiction rates to devices via shape subscriptions:

SUBSCRIBE SHAPE ON tax_rates WHERE jurisdiction IN ('US-CA', 'US-NY');

Lookup at invoice time with temporal query. Reconcile on sync if rates changed.

NodeDB-Lite Usage

// iOS
let db = NodeDbLite.open(path: "invoices.db")
db.execute("INSERT INTO invoices ...")
db.sync(url: "wss://origin.example.com/sync", token: authToken)

// Browser (WASM)
const db = await NodeDbLite.open("invoices");
await db.execute("INSERT INTO invoices ...");
await db.sync("wss://origin.example.com/sync");

All seven engines work locally with sub-millisecond reads. CRDT sync is transparent.