Business ID Integration at LY Corporation : Phased Migration for a B2B authentication platform with 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.

Transcript

1. 2026.06.29 LY Corporation LY Corporation ⼾⾼ 裕介 (Todaka Yusuke) Business ID Development Lead Business ID Integration at LY Corporation Phased Migration for a B2B Authentication Platform with Tens of Millions of Users
2. ⼾⾼ 裕介 Todaka Yusuke Business ID Development Lead 2018 Joined LINE Corporation Worked on LINE Official Account development 2021 Took charge of LINE Business ID development Present Business ID Development Lead
3. What is LY Corporationʼs Business ID? 1 Topics Business ID Integration Project Design 2 Project Retrospective 3 Business ID Integration at LY Corporation
4. What is LY Corporationʼs Business ID? 1 Business ID Integration Project Design 2 Project Retrospective 3 Topics Business ID Integration at LY Corporation
5. The login foundation for LY Corporationʼs B2B services What is Business ID?
6. DAU daily active users 1 Million+ Total Users users 30 Million+ Services services 50+ Scale of Business ID
7. What is LY Corporationʼs Business ID? 1 Business ID Integration Project Design 2 Project Retrospective 3 Topics Business ID Integration at LY Corporation
8. Company merger in 2023 Business ID Integration Motivation Yahoo! JAPAN Business Center LINE Business ID Yahoo! JAPAN Business ID Company Management Permission Management Billing Management Two Business IDs in One Company • LINE Business ID • Yahoo! JAPAN Business ID
9. Platform Integration Integrate two platforms into one unified platform. Account Integration Integrate two accounts into one unified account without losing their permissions. Business ID Integration Yahoo! JAPAN Business Center LINE Business ID Yahoo! JAPAN Business ID Company Management Permission Management Billing Management LINE Business ID Permission 1 Yahoo! JAPAN Business ID Permission 2 Business ID Business ID Permission 1 Permission 2
10. Business ID Integration Yahoo! JAPAN Business Center LINE Business ID Yahoo! JAPAN Business ID Company Management Permission Management Billing Management LINE Business ID Permission 1 Yahoo! JAPAN Business ID Permission 2 Business ID Business ID Permission 1 Permission 2 Platform Integration Integrate two platforms into one unified platform. Account Integration Integrate two accounts into one unified account without losing their permissions.
11. Business ID Platform Integration Policy Service-by-Service Authentication User Data Integration Switchover Migration
12. Business ID Platform Integration Policy Service-by-Service Authentication User Data Integration Switchover Migration To ensure a safe release, we divided the project into three steps, each with rollback capability.
13. New Business ID Web Yahoo! JAPAN Business Center Web Fetch data when required Users Authentication Integration LINE Business ID Data Yahoo! JAPAN Business ID Data Implemented Yahoo! JAPAN ID login
14. New Business ID Web Yahoo! JAPAN Business Center Web Fetch data when required Users Authentication Integration LINE Business ID Data Yahoo! JAPAN Business ID Data Implemented Yahoo! JAPAN ID login Yahoo! JAPAN Business ID users can now log in with their accounts without going through Yahoo! JAPAN Business Center.
15. Service-by-Service Switchover Yahoo! JAPAN Business Center API Yahoo! JAPAN Business ID Data Yahoo! JAPAN Business Center is used by more than 30 services. → A service-by-service switchover is being implemented over a two-year migration period.
16. Business ID API Yahoo! JAPAN Business Center API LINE Business ID Data Yahoo! JAPAN Business ID Data Switching API for Migration Service-by-Service Switchover
17. Business ID API Yahoo! JAPAN Business Center API LINE Business ID Data Yahoo! JAPAN Business ID Data Service-by-Service Switchover If an unexpected issue occurs, we can roll back at any time.
18. Business ID API Yahoo! JAPAN Business Center API LINE Business ID Data Yahoo! JAPAN Business ID Data Switch API for Migration Service-by-Service Switchover Migration Status • Halfway through the project timeline • Service migration in progress • 80% of active users are now on the new Business ID
19. Yahoo! JAPAN Business Center DB New Business ID DB User Data Migration The new Business ID must operate independently of Yahoo! JAPAN Business Center.
20. Yahoo! JAPAN Business Center DB New Business ID DB User Data Migration A userʼs data can be migrated once all services they are registered with have migrated to the new Business ID.
21. Yahoo! JAPAN Business Center DB New Business ID DB User Data Migration After the migration period, all user data will be migrated to the new Business ID.
22. What is LY Corporationʼs Business ID? 1 Business ID Integration Project Design 2 Project Retrospective 3 Topics Business ID Integration at LY Corporation
23. Success Point 1 Migrating Authentication First Yahoo! JAPAN Business Center LINE Business ID Yahoo! JAPAN Business ID Company Management Permission Management Billing Management Business ID
24. Success Point 1 Migrating Authentication First Yahoo! JAPAN Business Center LINE Business ID Yahoo! JAPAN Business ID Company Management Permission Management Billing Management Business ID Prioritizing the authentication feature on the roadmap helped: • Move the overall project forward • Make it easier for services to plan their migrations
25. Success Point 2 Enabling Rollbacks for Each Release Business ID API Yahoo! JAPAN Business Center API LINE Business ID Data Yahoo! JAPAN Business ID Data If an unexpected issue occurs, we can roll back at any time.
26. LINE Business ID Permission 1 Yahoo! JAPAN Business ID Permission 2 Business ID Permission 1 Permission 2 Area for Improvement Account Integration May Not Have Been Necessary
27. LINE Business ID Permission 1 Yahoo! JAPAN Business ID Permission 2 Business ID Permission 1 Permission 2 Area for Improvement Account Integration May Not Have Been Necessary A possible alternative would be multi-account login.
28. Summary Service-by-Service Authentication User Data Integration Switchover Migration
29. Summary Service-by-Service Authentication User Data Integration Switchover Migration To ensure a safe release, we divided the project into three steps, each with rollback capability.
30. 2026.06.29 LY Corporation LY Corporation ⼾⾼ 裕介 (Todaka Yusuke) Business ID Development Lead Business ID Integration at LY Corporation Phased Migration for a B2B Authentication Platform with Tens of Millions of Users