KakaoPay Insurance Pursues Legacy Module Removal and Spring Boot Upgrade via AOP-Based Shadow Comparison

KakaoPay Insurance (Kasonbo) shared the process of resolving legacy module dependency issues to upgrade a specific repository currently using Spring Boot 2.6 (targeting the latest 4.1). Dependencies on the existing product module were obstacles to the upgrade, but removing the legacy code was difficult until the MSA migration was complete.

AOP-Based Shadow Comparison Strategy

The development team adopted the Strangler pattern and introduced Shadow comparison logic based on AOP (Aspect-Oriented Programming). This approach returns responses from the existing logic for actual requests in the production environment while simultaneously executing the new logic to compare results.

• Ensuring Stability: Since the new logic is validated with production data, gradual migration can be led by developers without QA burden.
• Resource Optimization: The comparison logic runs asynchronously, and reflection calls are cached to minimize performance degradation.
• Monitoring: It is designed to be adjustable at runtime in case of memory or connection issues.

Implementation and Effects

The @ShadowInquiry annotation specifies the Bean and method to be compared, mapping the parameter indices of the existing and new methods. Through this, Kasonbo secured a safe migration path to simultaneously resolve two long-standing issues: removing legacy code and upgrading Spring Boot.