Designing an Easy-to-Use Toss Front SDK

Toss Place is developing an SDK for external integration partners to expand the ecosystem of Toss Front, its payment terminal. Since an SDK's first impression directly affects adoption and long-term maintenance, the key is to create a structure that makes it hard for users to make mistakes.

Rather than simply hiding functionality, the Facade pattern is applied to restructure complex internal implementations around the user's 'Intent'. For example, complex procedures such as server connection, message handler registration, and cleanup are abstracted into a single intuitive command like 'start server,' preventing human error.

For efficient design, low-level and high-level interfaces coexist.

• High-level (Facade): Handles the common use cases that make up 80% of overall usage, reducing cognitive load.
• Low-level (Escape Hatch): Provides fine-grained control to handle the remaining 20% of special requirements.

This design improves developer experience (DX) while also serving as a safeguard that structurally prevents memory leaks or failures caused by incorrect usage patterns.