Bank Salad iOS Team Cuts Build Time to 3 Minutes and Reveals Quality Management Strategy Through Modularization and TDD

Build Time Optimization and Development Efficiency

The Bank Salad iOS team significantly reduced build time by applying parallel builds through project modularization. On the latest MacBook, clean build time has been improved to about 3 minutes, and incremental build time to about 10 seconds. This is a notable improvement compared to the previous build time of roughly 5 to 7 minutes. However, in accordance with Amdahl's Law, parallel computing alone has limits to improvement, so the team adopted an approach of building only specific modules instead of the entire project.

Quality Management and Deployment Strategy

To ensure app stability, the team has established a Test-Driven Development (TDD) culture, and conducts internal beta testing for at least 2 weeks before release to preempt critical bugs. For emergency response, they use a gradual rollout strategy leveraging Feature Flags or experiments, and roll back immediately if issues arise. They have also applied the remote instant-improvement approach used in web serving services to iOS, increasing flexibility.

Post-mortems and Organizational Culture

The team emphasizes a post-mortem culture that treats incidents as opportunities for system improvement rather than blaming specific individuals. They use the 5 Whys technique to identify root causes and derive action items. They have also built a system that performs integrated UI tests on core logic such as sign-up and login, sending Slack notifications when failures occur. The iOS team aims to be "product development craftsmen" who handle not only development but also product planning, monitoring, and VoC analysis, and fosters a motivation-based work environment.