Building Kakao Pay's Credit Core with DDD (Domain Driven Design)

Kakao Pay decided to internalize its credit system, which had been operated using an external solution, for efficient maintenance and smooth communication. Considering the highly complex nature of credit business operations, the company adopted DDD (Domain Driven Design) as its design methodology to systematically manage the domain model.

The design proceeded in three main stages.

• Defining Bounded Context & Aggregate Root: The team clarified domain boundaries and established the Aggregate Root, a transaction unit for maintaining data consistency.
• Designing Domain Model & Function: The domain model was broken down into minimal units, and each domain was designed to be the sole controller of its own data, preventing side effects.
• Application Design: The team used PlantUML to visualize business flows and refined the design through reviews with team members.

This DDD-based design makes it easier to grasp business logic through domain objects even at the code level, helping to reduce system analysis time and improve maintainability.