Track a delivery with a trustworthy ETA

Define the user and system contract

A customer tracking page must show a useful ETA while the operations system retains authoritative trip state and late telemetry evidence. Record the region, data freshness, latency budget, privacy purpose, credential owner, and fallback before choosing an SDK or endpoint.

Create a durable trip identity

Bind order, route revision, provider trip, vehicle, and customer-safe tracking token before telemetry begins.

type AssetEvent = {
  id: string;
  assetId: string;
  occurredAt: string;
  type: "position" | "ignition" | "geofence.entered" | "geofence.exited";
  position?: { latitude: number; longitude: number; speedKph?: number };
};

export async function handleAssetEvent(event: AssetEvent) {
  // Idempotency matters: delivery may be retried.
  if (await events.exists(event.id)) return;
  await events.transaction(async () => {
    await events.record(event);
    await assets.apply(event.assetId, event);
  });
}

Process observations by event time

Deduplicate source events, store event and receipt time, reject state regression, map-match bounded fixes, and derive a new ETA revision only from eligible evidence.

Separate customer view from control state

Expose coarse progress and freshness without driver secrets or full history. Route exceptions to an owned operations queue before changing the promise.

Prove the production behavior

Automate the happy path and every named failure. The release is ready only when duplicate telemetry has one effect; late evidence remains auditable without rewinding progress; closure requires provider acknowledgement and delivery proof. Capture provider request identity without logging credentials or unnecessary precise location.

Failure modes you must exercise

Definition of done

REST production checks

Continue from source, contracts, and a full app

These links resolve to repository-derived evidence; unsupported package names and endpoints are not filled in from guesswork.