Build an application that synchronizes external data

What you will build

An application that imports records from an external API and reports every synchronization run.

Part 1: Plan the application

Define an external stable ID, mapped fields, update rules, deletion policy, and a SyncRun record with timestamps, counts, cursor, and outcome.

Part 2: Connect the API

Store the credential as a secret. Fetch one page on the server, validate it, and display a read-only preview.

At this point, one validated API page appears without storing records.

Part 3: Store records idempotently

Upsert by external ID and record created, updated, skipped, and failed counts. Repeating the same page must not create duplicates.

Part 4: Add pagination and scheduling

Handle the API’s cursor, page, or offset scheme. Add a scheduled job in code with bounded retries and rate-limit backoff. Include a development-only run-now path.

At this point, two identical runs produce the same records and separate successful run history.

Part 5: Test failures

Test an expired credential, rate limit, malformed record, and interrupted page. Confirm each failure is logged and can resume safely.

Part 6: Deploy

Deploy with production credentials, invoke one controlled run, and confirm its SyncRun result.

Extend the application

Add webhook updates, drift reports, or a manual reconciliation queue.