How to sync large amounts of contacts from the HubSpot API

Building API integrations with HubSpot can be challenging, particularly when syncing more than 10,000 contacts from a customer's portal. This process involves creating a durable, resumable sync that only fetches new or changed records, managing numerous user authentication tokens, and handling webhook updates. The guide outlines a method to develop a production-ready HubSpot contacts sync using AI Coding Agents like Claude Code, Cursor, Codex, and the Nango AI Function Builder skill. It suggests a two-phase sync strategy utilizing both HubSpot's basic list endpoint, which has no cap but lacks filtering capabilities, and the search endpoint, which filters by lastmodifieddate but is limited to 10,000 results. The integration requires managing durable checkpoints, resumable execution, OAuth lifecycle, and rate limits, all of which Nango provides through its managed integration platform. The guide also offers a step-by-step process to implement a contacts sync, including setting up OAuth app credentials, deploying the sync, and handling sync-completion webhooks, demonstrating how Nango simplifies the integration process across various APIs.