Backend Developer (Django)

DeWarmte; Den Haag; On-site; EUR 56,000 - 73,000; Full time

Benefits offered by this job

Daily lunch at the office

SAR programme

27 vacation days

8% holiday allowance

Laptop and AI tools access

Job summary

DeWarmte is building the connected backend powering its heat pumps, mobile and web apps, and data platform. As Backend Developer you’ll write production Python/Django code, design and deploy new APIs, and help the platform scale with the growing customer base.

You’ll ensure reliability, security, and performance, diagnose cross‑system issues, and collaborate with hardware, data and product teams. With AI tools in the mix, you’ll raise quality while keeping standards high.

Qualifications

• Solid hands-on backend experience with production systems.
• Deep Python and Django expertise, including REST APIs.
• Strong knowledge of relational databases (e.g., PostgreSQL).
• Experience with CI/CD, testing, observability and incident handling.
• Ability to learn and operate in IoT/product environments.

Responsibilities

• Develop and improve our Django backend
• Design, build, test and deploy new APIs, services and business logic
• Improve performance, stability, security and data integrity
• Diagnose and fix cross-system issues spanning backend, data platform and devices

Skills

Python

Django

REST APIs

PostgreSQL

CI/CD

AI tools

Tools

Django ORM

DRF

Job description

At DeWarmte, we make smart, affordable heat pumps that help homes move away from gas. We design the hardware, software and services ourselves, so the quality of our software directly shapes how well our products work in people's homes.

We're growing fast. More customers, more connected heat pumps and more products relying on our backend mean the platform needs to grow with us. That's why we're looking for a Backend Developer to build and improve the Django platform behind our web application, customer app and employee app. It connects these products with our heat pumps, data platform and external partners.

You’ll spend most of your time writing code: improving reliability and performance, building new functionality and helping the platform scale with our customer base and installed fleet.

AI tools are already part of how we build software. We use them where they help us move faster, but we do not lower the bar: anything we ship still needs to be secure, maintainable and correct. You'll help us get better at both.

Why this role matters

Build the connected intelligence behind DeWarmte—linking our heat pumps, digital products, internal systems and smart‑home partners to make every installation smarter, more efficient and easier to use.

You’ll join the team behind backend systems that already support customers and heat pumps in the field. You'll get to know them deeply, keep them reliable and evolve their architecture as DeWarmte grows. Just as important: you'll help make sure knowledge and operational ownership are shared across the team.

What you'll do

Develop and improve our Django backend

• Work directly in the production Python/Django code behind our web application, customer app and employee app.

• Design, build, test and deploy new APIs, services and business logic, covering everything from the customer journey and planning to heat pump control and service.

• Improve performance, stability, security and data integrity.

• Diagnose and fix issues that span our backend, data platform and devices in the field.

Connect and scale the platform

• Make sure our backend, databases and background processing keep up with a fast-growing customer base and installed fleet.

• Connect our backend with our heat pumps, data platform, web application, mobile apps, internal tools and smart‑home platforms such as Homey, Home Assistant and HomeWizard.

• Define clear, well‑documented interfaces between device software, cloud services and the products that depend on them.

• Put the right automated testing, observability, monitoring and release practices in place.

Build with AI

• Use AI tools to support design, coding, testing, reviews and documentation.

• Help the team improve its AI workflows, shared context and quality checks.

• Try new tools, keep what works and share what you learn.

• Hold AI‑assisted code to the same standards as any other production code.

Share ownership

• Turn implicit knowledge into clear documentation, tooling and repeatable engineering practices.

• Design systems that other engineers can easily understand, test and safely change.

• Take part in code reviews and technical decision‑making.

• Help onboard and support fellow engineers.

Work across the company

This role reaches across the product. You'll work with colleagues in web, apps, hardware, controls, data, product development, installation and service to solve today's issues without compromising the platform for tomorrow.

What success looks like

In your first few months

• You understand the existing backend, its data flows and its operational risks.

• You can independently maintain, debug and release backend changes through the team's review and release practices.

• The most important technical risks and knowledge gaps are visible and prioritised.

• Monitoring, documentation and development practices are visibly improving.

As the role develops

• New backend functionality ships predictably and safely.

• The platform scales smoothly as our fleet and customer base grow.

• Incidents are detected early and resolved in a structured way.

• The team uses AI tools confidently and responsibly in its day‑to‑day work.

• Critical backend systems are understood and maintained by more than one person.

Who we're looking for

• Solid hands‑on backend engineering experience, including ownership of production systems.

• Deep Python and Django expertise, including the Django ORM and REST APIs (e.g. Django REST Framework).

• Strong knowledge of relational databases (e.g. PostgreSQL): data modelling, query optimisation and migrations.

• Experience with background processing, queues or event streaming, and with integrating external systems.

• A track record of taking functionality from design through implementation, testing and deployment to real‑world operation.

• Strong engineering fundamentals: version control, automated testing, CI/CD, observability and structured incident handling.

• You use AI coding tools in practice and understand both their value and their limits.

• The ability to bring clarity to an environment where systems and processes are still taking shape.

Experience with IoT, connected devices, telemetry, time‑series data such as Kafka or InfluxDB, or cloud infrastructure is useful, but not essential. What matters most is that you can learn a complex physical product and take responsibility from code to production.

How you work

• You fix urgent problems without letting short‑term workarounds become long‑term architecture.

• You explain complex technical topics clearly to people from any background.

• You balance reliability today with the investments needed to scale tomorrow.

• You're curious about new AI tools, try them quickly and share what works.

• You're comfortable switching between debugging a production issue, reviewing architecture and helping a teammate.

• You share knowledge by default and care about what the team can own together.

What we offer

• A role with direct impact on the backend systems at the heart of a real physical product and the energy transition.

• The chance to shape a fast‑growing platform and how we build it.

• Room to improve how we use AI tools across the software team.

• A gross monthly salary of [€5,000 – €6,500], based on full‑time employment.

• 27 vacation days and 8% holiday allowance.

• The chance to share in DeWarmte's growth through our Stock Appreciation Rights (SAR) programme.

• An ambitious, collaborative team and real responsibility from day one.

• Daily lunch at the office.

• A laptop, access to the AI tools we use and everything else you need to do your best work.

• Regular team activities, including our annual Beach Day and Winter Trip.

• Plenty of room to grow, develop yourself and make a lasting impact.

Interested?

Want to build the connected intelligence behind DeWarmte's heat pumps? We'd like to meet you.