Adapter

Adapter wraps a third-party or legacy dependency behind the interface your application already expects. Translation covers method names, error shapes, pagination models, and async semantics. Good adapters are thin: they map protocols without re-implementing business rules.

On interviews: give an example adapting a vendor SDK to your repository port. Explain where mapping belongs versus domain services.

Common pitfalls: adapters that grow into business logic dumps; leaking vendor types through the port; one adapter reused for unrelated contexts.

The trade-off is flexibility versus complexity—know when the simpler path is enough.

Checklist:

• Define the target port before writing adapter.
• Map errors to application-level result types.
• Keep adapter stateless when possible.
• Test adapter with recorded vendor fixtures.