Python / Django Developer

Python / Django Developer - Vacature | Swishfund

We are looking for an experienced Python/Django developer to maintain and improve Calmstone, our core lending and loan administration platform. Be open, flexible and eager to learn.

Calmstone powers the full loan lifecycle across the Netherlands and the United Kingdom — from application intake and credit assessment through contract generation, digital signing, payment collection, and ongoing loan servicing. You will work on a production system that integrates with banking APIs, credit bureaus, and CRM platforms, handling real financial data and regulatory requirements.

Calmstone uses server-side rendering with Django templates, jQuery, and Bootstrap for the frontend, and connects to MySQL databases (including a Snowflake data warehouse for analytics).

Maintain, and improve the existing Django codebase across all apps, ensuring stability and reliability of the production platform

Build new features and modules to support business growth, including expansion into additional market

Improve code quality through refactoring — for example, migrating legacy JSON-based data structures to proper Django.

Write and maintain tests to increase coverage and confidence in deployments

Optimise database queries and application performance across the multi-database architecture (MySQL, Snowflake)

Contribute to the CI/CD pipeline and Docker-based deployment infrastructure on AWS Requirement.

3+ years of professional experience with Python and Django in a production environment

Strong understanding of relational databases, particularly MySQL, including query optimisation and migrations

Experience working with RESTful APIs — both building and consuming them

Familiarity with Docker and containerised deployment workflows

Experience with Git and CI/CD pipelines (GitLab CI preferred)

Comfortable reading and working with a large existing codebase

Experience with payment processing systems or banking API integrations (SEPA, direct debits)

Familiarity with credit bureau data and scoring models

Knowledge of Django REST Framework (DRF) and API documentation tools (Swagger/OpenAPI)

Experience with Redis, Celery, or django-background-tasks for async job processing

Frontend skills: jQuery, Bootstrap, D3.js, or willingness to work with legacy frontend code

Experience with AWS services (S3, EC2, ECR) and infrastructure management

Familiarity with Prometheus/Grafana for monitoring and observability

Knowledge of data analysis tools: pandas, NumPy, scikit-learn

Dutch language skills are a plus but not required

A meaningful role working on a production financial platform with real impact

Ownership and autonomy over the technical direction of the application

Flexible working arrangements (hybrid within the Netherlands)

A collaborative team environment with room to grow

Send your CV and a brief motivation to our hiring team. We look forward to hearing from you.

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