API Developer

Brussel · Voltijds

Over de functie

Mission Overview

We are seeking an API Developer for a consultancy mission at a client site, representing Keystone Solutions. The objective is to re-implement a subset of a third-party API to ensure a smooth transition for current users. This role involves working on a straightforward API with two main functional parts: a metadata layer and a submission layer.

Key Responsibilities

  • Analyze the existing API and its documentation, and agree on the subset to cover.
  • Analyze the ODS database and map its metadata to what the existing API exposes, identifying any gaps.
  • Propose and implement a security approach (authentication, authorization, secure handling of submitted data), highlighting where it differs from the current API.
  • Implement the metadata endpoints on top of the ODS database.
  • Implement the submission endpoints, with validation of submitted data and meaningful error responses.
  • Hand over submitted data to the ODS loading code (or store it in the form that code expects).
  • Write automated tests and concise technical documentation.
  • Deploy and demonstrate the solution on Ubuntu Linux.
  • Report on limitations, open questions, and recommended next steps.

Required Skills

  • Python 3.12+ with FastAPI.
  • SQLAlchemy and PostgreSQL (reading and mapping an existing schema).
  • REST API design.
  • API security: authentication and authorization (e.g. OAuth2/OIDC, JWT, API keys), TLS, input validation.
  • Automated testing (pytest).

Nice to Have

  • Polars in combination with SQLAlchemy.
  • uv for package management.
  • Experience with API compatibility or migration projects.
  • Experience handling sensitive data (e.g. health data) and GDPR requirements.
  • Linux deployment experience.

Soft Skills

  • Autonomy and ability to work from incomplete documentation.
  • Pragmatism: focusing on the critical parts first while keeping quality high on what is delivered.
  • Clear communication of findings and limitations.

At Keystone Solutions, we pride ourselves on our consultancy nature, offering dynamic projects that provide turbo-charged learning opportunities. As a

Duration: 26/10/2026 - 31/12/2026 3 months • (full time)

Skills required

  • APIExpert
  • API DesignExpert
  • API Developer experience (SOAP en REST)Expert
  • API development (FastAPI,...)Expert
  • API Security a.d.h.v. OAuth en WS-SecurityExpert
  • PostgreSQLExpert
  • PytestExpert
  • PythonExpert
  • RESTExpert
  • SQLAlchemyExpert

Language requirements

  • NederlandsPassieve kennis
  • EngelsActieve kennis
  • FransPassieve kennis

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