API Developer

Keystone Solutions; Brussel; À distance; EUR 70 000 - 110 000; Plein temps

Résumé du poste

Keystone Solutions in Belgium is seeking an API Developer for a client-site consultancy to re-implement a subset of a third-party API, including a metadata layer and a submission layer. You will analyze the existing API and the ODS database, implement metadata and submission endpoints, ensure secure handling of data with OAuth2/JWT/TLS, write tests and documentation, and deploy on Ubuntu.

The role emphasizes autonomy, pragmatism and clear communication, with a 26/10/2026 to 31/12/2026, full-time

Qualifications

• Expertise in API design (REST) and FastAPI.
• Strong PostgreSQL knowledge and SQLAlchemy mapping.
• Experience with API security (OAuth2/JWT/TLS).
• Experience with automated testing using pytest.

Responsabilités

• Analyze the existing API and map metadata to the new subset.
• Map ODS metadata to API exposure and identify gaps.
• Propose and implement security approach (authn/authz, TLS) and differences from current API.
• Implement metadata endpoints on top of the ODS database.
• Implement submission endpoints with data validation and meaningful errors.
• Pass submitted data to the ODS loading code or store it in the expected format.
• Write automated tests and concise technical documentation.
• Deploy and demonstrate the solution on Ubuntu Linux.
• Report limitations, open questions, and next steps.

Connaissances

Python

FastAPI

SQLAlchemy

PostgreSQL

REST API design

API security

pytest

Outils

uv

Description du poste

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.

Duration

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

Skills required

• API - Level: Expert - Most recent: Any time
• API Design - Level: Expert - Most recent: Any time
• API Developer experience (SOAP en REST) - Level: Expert - Most recent: Any time
• API development (FastAPI,...) - Level: Expert - Most recent: Any time
• API Security a.d.h.v. OAuth en WS-Security - Level: Expert - Most recent: Any time
• PostgreSQL - Level: Expert - Most recent: Any time
• Pytest - Level: Expert - Most recent: Any time
• Python - Level: Expert - Most recent: Any time
• REST - Level: Expert - Most recent: Any time
• SQLAlchemy - Level: Expert - Most recent: Any time

Language requirements

Dutch

Level Passive knowledge

English

Level Active knowledge

French

Level Passive knowledge