Reconciliation

Snapshots are truth. Reconcile against them on a schedule, independent of whether webhooks arrived.

The sweep

Run it on a timer, and again after any deploy or outage:

• Sweep the order book. GET /v1/orders?status=... lists your non-terminal orders; check each against its snapshot so a missed webhook never becomes a stuck order.
• Recover per order. GET /v1/orders/{id} returns the authoritative snapshot including last_seq; GET /v1/events?order={id}&after_seq={n} replays what you missed.

Delivery actuals

Aired counts and delivered impressions come from the seller as delivery_post artifacts on the order: per-unit, per-week actuals in the declared currency, source-tagged. Audience guarantees reconcile against them; the platform carries the numbers, it never computes them.

Files and EDI

Sellers who live in traffic systems return actuals as the industry's own paper: station-generated EDI invoices and as-run log times land through the file interface and reconcile against orders, so billing stays in the systems both sides already trust.