Nylas has enhanced its Contacts API by introducing a new version, Contacts v2.0, which now provides full CRUD capabilities and synchronization, enabling businesses to manage and integrate contact data more comprehensively. Previously limited to read-only functionality, the updated API supports additional fields such as multiple email addresses, job titles, and physical addresses, allowing for richer data management. The development process included expanding the contact model, adding new API endpoints, and updating their NodeJS SDK to support these changes. The implementation involved deploying changes under a feature flag to minimize disruptions for existing customers, with extensive testing and feedback gathered through an open beta phase. This update also prompted a strategic decision to version the API, balancing the need for iterative product evolution against potential challenges for customers in updating to new versions. This approach aims to enhance user experience while maintaining a clean and sustainable engineering architecture.