Merpay's Payment Platform team describes a new abstraction called Exchange to unify fragmented payment APIs. Instead of separate APIs for payments, top-ups, transfers, and partner settlements, Exchange models any fund movement as a source-to-destination operation with a two-phase Authorize/Capture lifecycle. The design introduces a Value concept to unify payment methods and destinations, passes accounting codes through the API to eliminate hardcoded accounting logic, and uses a Saga pattern for failure compensation in distributed transactions. Extension points (Hooks, Steps, Decisions) allow product teams to inject use-case-specific logic like KYC checks without polluting the core. The goal is to reduce coordination overhead, clarify API responsibilities, and enable faster onboarding of new payment use cases.
