API Design & Development

Contract tests generated from the OpenAPI specification run on every commit, so a removed field or a narrowed type fails the build rather than a partner's integration. Consumers can register their own expectations, which are executed against each candidate release. Before a public change we publish the diff, run both versions in parallel and agree a deprecation window with named consumers.

Yes. The usual route is a facade: we model the resources and operations consumers actually need, publish the specification, then implement it over the existing application while its internals stay as they are. Business logic is extracted behind that contract incrementally. This avoids a rewrite and gives integrators a stable interface even while the system underneath is still changing.

The OpenAPI or GraphQL schema as the source of truth, the implementation, contract and load test suites, generated client SDKs, reference documentation with a sandbox, and gateway and rate-limiting configuration as infrastructure code. Everything sits in your repositories. Where the API is public we also deliver the versioning and deprecation policy in writing, because that is what integrators plan against.

The drivers are the number of resources and operations, whether data comes from one system or several, the depth of authentication and permission logic, and whether the API is internal or public — public APIs carry documentation, sandbox and support obligations that internal ones do not. We price the design and specification phase separately from implementation, so scope is defined before you commit to the build.