Backend Elixir developer

We are seeking a skilled Backend Developer to join our team and contribute to the development of web applications, APIs, and backend systems. You will work with cutting-edge technologies, primarily Elixir, PostgreSQL, and GraphQL, to create robust and scalable backend solutions that power our digital projects.
  • Available for 32 - 40 hours
  • min. BSc
  • passion for the profession!
  • MSc
  • experience with Elixir

This vacancy has been filled. Please send your open application with CV to

Are you a recruiter? We are not interested!

About the position

Are you a talented Backend Developer looking for an exciting opportunity to work with cutting-edge technologies and be a part of a dynamic team in the heart of Delft, The Netherlands? If you're passionate about software development and want to make a significant impact on the digital world, then 9to5 software is the place for you!


  • Design, develop, and maintain backend systems using Elixir and PostgreSQL.
  • Collaborate with our team of backend and frontend developers and designers to deliver high-quality web and mobile applications and APIs.
  • Implement and optimize GraphQL APIs to ensure efficient data retrieval.
  • Write clean, well-documented, and maintainable code.
  • Troubleshoot and debug issues, ensuring the performance and reliability of backend systems.
  • Stay up-to-date with industry trends and best practices in backend development.
  • Contribute to code reviews and provide constructive feedback to team members.
  • Participate in agile development processes and sprint planning.


  • Proven experience as a Backend Developer, with a focus on Elixir and PostgreSQL.
  • Strong knowledge of GraphQL and its implementation.
  • Proficiency in software development best practices, including Git and automated testing.
  • Familiarity with frontend technologies (HTML, CSS, JavaScript) is a plus.
  • Problem-solving skills and the ability to work effectively in a collaborative team environment.
  • Excellent communication and interpersonal skills.
  • Bachelor's degree in Computer Science or related field (or equivalent experience).

Besides an inspiring working environment, we offer the following employment conditions:

  • Unlimited holidays
  • MacBook Pro, which you can also use at home
  • A 32-inch 4K screen at your own workstation
  • Possibility to work at a sit/stand desk
  • Lunch and drinks at 9to5's expense
  • Flexible working options: hybrid or full-time at the office
  • Travel allowance based on €0.21 per kilometre if you live more than 5 km from our office.

We look forward to hearing from you and welcoming you to our team!

Working at 9to5

At 9to5 you work in a small team of software engineers. Tom and Susan started the company in 2012 after their education at TU Delft and are actively participating in the development of the software. We have UX / UI designers and web, Android, iOS and back-end developers in-house. As a result, we often work on a project with the entire team. We are all in one room and often work hard and concentrated, but there is also time for fun. Dress code is casual, but representative.
On an average working day you arrive between 8:30 am and 9:00 am, we have a standup at 9 am and we get to work. Around 10 am it is time for coffee with a cookie and then continue working until lunch. Lunch is shared and delivered weekly at the cost of 9to5. After lunch we work until 5:00 PM to 5:30 PM. Is it a Friday? Then the day will end with a nice drink anyway, but that is not excluded on any other day.
Hardware at 9to5
  • MacBook Pro (or what you like)
  • 4K display
  • Laptop stand
  • Apple Magic Mouse or Trackpad
  • Bureau - adjustable in height
Software at bij 9to5
  • Google Workplace
  • Jira - for project management
  • Slack - to chat with each other and clients
  • Bitbucket - version control
  • Harvest - time tracking

This vacancy has been filled. Please send your open application with CV to

Are you a recruiter? We are not interested!