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OpenAPI / Swagger Development

Professional OpenAPI / Swagger development from experienced developers based in Graz, Austria.

At dectria, we follow an API-first approach. OpenAPI (formerly Swagger) is the standard for API design, documentation and code generation. Every API we build starts with a specification.

In practice, we write the OpenAPI specification first — as the single source of truth for the entire API. From this spec, we generate type-safe clients for the frontend and type-safe interfaces for the backend. Redocly serves as interactive documentation for integration partners. This way, frontend and backend teams work against the same contract from day one.

API-first means the contract is defined before implementation - frontend and backend teams can work in parallel, integration partners get documentation from day one and API changes are versioned and backward-compatible.

Official website

Capabilities

What We Build with OpenAPI / Swagger

API-First Design OpenAPI 3.x Specification Redocly Documentation Type-Safe Code Generation (Frontend & Backend) Client SDK Generation API Versioning Schema Validation Mock Server Generation CI/CD API Testing Contract-First Development

Use Cases

Typical Use Cases

API Design & Documentation

Contract-first approach with auto-generated interactive docs - the API contract is defined before the first line of code is written.

Third-Party Integration

Self-documenting APIs that external partners can integrate without support overhead - with interactive documentation and generated client SDKs.

API Modernization

Documenting and standardizing legacy APIs as part of modernization projects - existing interfaces are enriched with OpenAPI specifications and made future-proof.

References

Selected Projects

Klanglicht Audio Guide
Web Application

Klanglicht - Art Festival of Bühnen Graz

Klanglicht Audio Guide
Soundportal App
Mobile App

Radio Soundportal

Soundportal App
Deposit Insurance Payout Platform
Web Application

Österreichische Raiffeisen-Sicherungseinrichtung eGen (ÖRS)

Deposit Insurance Payout Platform
View all references

FAQ

OpenAPI / Swagger FAQ

Why does dectria follow an API-first approach?
API-first means we define the API contract before starting implementation. This enables parallel work between frontend and backend teams, gives integration partners reliable documentation immediately and ensures APIs are consistent and well-designed.
How does auto-generation work with NestJS?
We write the OpenAPI specification first and generate type-safe clients for the frontend and interfaces for the backend from it. The spec is published as interactive documentation via Redocly. Changes to the API always start with an update to the specification — ensuring code and documentation stay in sync.
Can you document existing APIs?
Yes, we also document and standardize existing APIs retroactively. We analyze the existing endpoints, create OpenAPI specifications and set up automated validation to ensure the documentation stays current long-term.

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