LINE and Yahoo! Business ID Integration: The Path to Non-Disruptive Integration of B2B Authentication Infrastructure for Tens of Millions of Users

On June 30, 2025, LINE Business ID and Yahoo! JAPAN Business ID were integrated into a single Business ID.
LINE Business ID is a B2B ID platform with tens of millions of accounts. Each system, covering authentication, authorization, account management, and external integration, had its own unique history and design philosophy.

In this session, we will introduce the technical challenges we faced in integrating two large-scale authentication platforms without disrupting service, and our approach to solving them.

• Integrating different authentication platforms (session management, token design, and ID system)
• Preventing data inconsistencies during account integration
• Phased rollout design to enable gradual migration
• Designing a migration path that preserves the user experience
• Rollback strategies to minimize the risk of failure

This session will not simply discuss system integration, but will share practical knowledge from the technical to product layer, focusing on how to design and safely proceed with large-scale ID integration.

Engineers involved in large-scale service integration, ID infrastructure renewal, and post-M&A system integration will learn reusable design patterns and the inside story of decision-making.