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Senior Frontend Engineer (React) in Amsterdam


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Job Description

We are one of the fastest growing HealthTech companies, having tripled our customer base in the last year. We are proud of the fact that our customers are our biggest growth engine. Our goal is to ensure the world’s research data becomes reusable and machine readable. To get there we’re tackling interesting challenges in scalability, security, machine learning, cryptography and UX. To be successful we need to continuously improve and grow our product. We believe we can accomplish this with a healthy, happy, world-class team that is looking to make an impact.

We are looking for an experienced frontend developer that wants to contribute to science while working in a challenging commercial environment.

The main challenges

  • Designing the architecture for our new React frontend application that will impact the daily life of thousands of researchers

  • Working with our UX team to translate user requirements into beautiful new functionality

  • Teaching and mentoring other engineers about Javascript

The daily responsibilities:

To keep our products at the frontier of innovation, your responsibilities will include:

  • Migrate components from our ExtJS (3.4 / 6.5) projects to React

  • Creating scalable design systems and pattern libraries

  • Collaborating with engineer, product and customer success teams.

  • Investigating and building automated unit-, functional and acceptance tests

  • Identifying opportunities for process and tool improvements and implementing them

  • Working on automated toolchains to build and integrate our application


To be successful in your role you (mostly likely) have 5+ years of experience with building up large-scale frontend javascript applications from scratch, preferably using React. You prefer high quality, well-structured code over quick fixes and hacks and educate yourself to stay up to date of dynamic landscape of Javascript libraries and frameworks. You are excited to help us scale from NL to EU to global, making sure all our customers have the best user experience and you relish the opportunity to help us with automated testing, security and Continuous Delivery.

  • 5+ years of Javascript experience, 2-3 years of React experience

  • You have designed and developed large (enterprise) applications

  • You have experience with ExtJS, or are willing to learn its architecture

  • You have experience with creating scalable design systems and pattern libraries

  • You have a strong customer focus

  • You have strong verbal and written communication skills

What does working at Castor include?

  • The opportunity to help us improve medical research and healthcare

  • A strong growth path in a scale-up with a budget to encourage personal development

  • A good benefit package, including team bonus, pension, travel expenses and fun outings

  • 30 vacation days per year, on top of Dutch public holidays (6)

  • Possibility to participate in our stock option plan

  • Healthy lunch, snacks and Friday afternoon drinks

Start: prefered June/July

Availability: 32+ hours per week. On-site

Contact: Taru Saares (People and Operations Specialist)

Our stack and tools

We will build a new React-based frontend, currently we use Sencha ExtJS 3.4 and 6.5 for Frontend. For our redesign we will be applying Brad Frost's Atomic Design Methodology. The backend consists of PHP7 applications using Zend Framework 2 and Doctrine 2, backed by multi-tenant MySQL/MariaDB databases.

Our toolset includes Slack, JIRA, Bitbucket, Confluence and Google for Business. We use Jenkins as a continuous integration server.

About us

Delivering the best possible healthcare to patients worldwide requires an efficient research process that drives innovation in healthcare. Currently, 85% of resources spent on medical research do not contribute to patient health. At Castor we are creating user-friendly technology that solves these issues. Founded by an MD PhD, we understand that researchers want technology to work for them, not against them.

Our goal is to ensure the world’s research data becomes reusable and machine-readable so that we can leverage the power of AI to help us solve the biggest healthcare challenges. To be successful, we need to continuously improve and grow our product. We believe we can accomplish this with a healthy, happy, world-class team that is looking to make an impact.


About Castor

  • Healthcare

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