# ADR: Payment Boundary

## Context
In our architecture, we aim to define the boundaries of the payment domain. This is vital for ensuring that our system is modular and easily maintainable. The payment process will interface with external gateways while keeping the core business logic separate from these integrations.

## Decision
We have decided to place the external payment gateway behind a port interface. This allows us to decouple our domain logic from the specific implementations of payment providers, thus making it easier to adapt to changes in external systems.

## Alternatives
1. **Direct integration with payment gateways:** This approach would tightly couple our domain layer with external systems, making changes difficult and increasing risk.
2. **Using an event-driven architecture:** While this could provide more flexibility, it introduces complexity and may lead to challenges in ensuring consistency.

## Consequences
By implementing this boundary, we gain the ability to change payment providers with minimal changes to our internal domain logic. However, we must carefully manage the interfaces and ensure that they are well-defined and stable to avoid integration challenges in the future.