KakaoPay's Account Token System Overhaul: A Swift Concurrency Use Case

KakaoPay operates a token system across various environments, including the Pay service within KakaoTalk and a separate app. The existing system suffered from issues such as missed processing when tokens were requested concurrently, and unnecessary defensive code caused by fragmented token access code.

To address this, token-related logic was encapsulated into a separate module, and the asynchronous processing environment was improved. In particular, the Swift Concurrency async/await model was actively utilized to improve code readability and stability.

By adopting Swift Concurrency, the following long-standing problems were resolved:

• Completion Hell: Solved the readability degradation caused by nested closures
• Missing Completion: Prevented missed callback calls that used to occur when using guard or if let
• Stronger Error Handling: Enforced try/catch at the compiler level to prevent missed error handling

Through this overhaul, asynchronous workflows can now be written as intuitively as synchronous code, and an environment has been established where missing error handling can be prevented at compile time.