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JS Ninja

Amsterdam, Netherlands

Job Type

Full Time (38hrs/w)



We are seeking a talented and ambitious JavaScript Ninja to join our innovative startup. If you're passionate about cutting-edge technologies and want to contribute to the growth of a dynamic team, this role is perfect for you. As a JavaScript Developer, you will have the opportunity to shape and enhance our fintech products, delivering impactful solutions in a rapidly evolving industry. You must be fluent in English, and have proven experience building JS applications, both Front and Back.

We work flexibly, on average 2d/w at the office, without strict locations. We have our offices in Amsterdam, Brussels, and Heerlen.


In this role, you’ll be responsible for designing, building, and maintaining Hyfen’s state of the art software services. You will work in one of our project teams to write reusable, testable, and efficient code and to implement high-availability applications. You’ll be responsible for ensuring the proper respect of security practices and data protection. You’ll be expected to discover, plan, develop, document, and maintain new and existing integrations and endpoints. You will have a key responsibility in our 24/7 operations, and be one of the drivers for the software architecture, tooling, and integration strategy choices made by HYFEN.

Concretely, we’ll expect you to :

  • Design, build and maintain our software services

  • Integrate user-facing elements developed by front-end developers with server side logic

  • Build reusable code and libraries for future use

  • Optimize applications for maximum efficiency and scalability

  • Implement security and data protection

  • Design and implement data storage solutions

Must Have Skills

Concepts & Principles

  • Software architecture and security best practices / standards

  • Authentication and authorization between multiple systems, servers, and environments

  • Integration of multiple data sources and databases into one system

  • Database schemas (aligned with business processes)

  • Automated testing platforms and unit tests

  • Code versioning

  • OWASP security principles

  • Certificates & SSL, CORS

  • Interfacing via REST APIs (incl. designing API Flows & Writing Specifications)

  • Setup and administration of backups

  • Networking (incl. DNS, Encryption, VPN, firewalls, reverse proxies, …)

  • Agile and Scrum

Operating Systems:

  • MacOS or Windows

  • Linux


  • Microsoft Azure

  • Github Actions (developing and using)

  • NodeJS

  • React 

  • Containerization (Docker)

  • Kubernetes

  • Databases (MySQL)

  • Version Control (git)

  • Visual Studio Code

The Cherry on top

You’d really stand out if you have experience with:

  • Kubernetes

  • Helm

  • Cert Manager

  • Ingress Controllers

  • Database Migration

  • Prometheus (and Grafana)

  • Elastic Stack (ELK)


We are looking for someone dynamic, a team player at heart, eager to learn, and ready to jump on new topics while taking ownership in delivery.


Thanks for submitting!

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