Sr. Full-Stack Developer

twentysix; Hilversum; On-site; EUR 65,000 - 90,000; Full time

Benefits offered by this job

Diverse and inclusive work environment

Career growth opportunities

Job summary

twentysix is looking for a skilled Sr. Full-Stack Developer located in Hilversum, Netherlands. The role involves developing and maintaining our proprietary orchestration platform, focusing on both frontend and backend development to enhance performance and user experience.

The ideal candidate will have expertise in ReactJS and PHP/Symfony, ensuring high-quality web applications and integrations with third-party services. A collaborative mindset and the ability to adapt to new technologies are key to success in this role.

Join us in shaping the future of digital marketing and technology!

Qualifications

• Strong proficiency in ReactJS and TypeScript with experience in responsive design.
• Experience with PHP and MVC frameworks like Symfony.
• Proven experience in API design and integration.

Responsibilities

• Develop and maintain responsive web applications using ReactJS and TypeScript.
• Design and document secure RESTful APIs.
• Debug and resolve complex full-stack issues.

Skills

ReactJS

TypeScript

JavaScript (ES6+)

HTML5

CSS3

PHP

Symfony

REST API design

Agile development

Education

3-5+ years of professional full-stack web development experience

Tools

AWS

GCP

Docker

Job description

Please note that we will never request payment or bank account information at any stage of the recruitment process. As we continue to grow our teams, we urge you to be cautious of fraudulent job postings or recruitment activities that misuse our company name and information. Please protect your personal information during any recruitment process. While Monks may contact potential candidates via LinkedIn, all applications must be submitted through our official website monks.com/careers.

Sr. Full-Stack Developer

Employment Type: Full-Time

Experience Level: Senior

Industry: Technology, Digital Marketing, Web Development

About Monks

Monks is the industry’s Agentic Transformation Partner, architecting the future of real‑time brands. As a global marketing and technology services company, we go beyond traditional boundaries to design and operate Agentic Operating Systems that help brands innovate, organize, and operate at the speed of culture.

At Monks, we value T‑shaped talent—people with deep craft mastery and a horizontal fluency in AI that allows them to collaborate across disciplines and deliver outcomes. With a global team of nearly 6,000 digital experts across 33 countries, you’ll find a diverse group of colleagues with different backgrounds and perspectives. We believe everyone has something of value to offer, and that sustaining a truly diverse, equitable and inclusive workplace begins with fostering an environment where people can be themselves, authentically, every day.

Job Summary

We are seeking a highly skilled Full‑Stack Developer to drive the evolution of our proprietary central orchestration platform. In this role, you will bridge the gap between practical user experience and powerful server‑side logic, helping us scale the internal tooling that enables our teams to operate more effectively and competitively.

The ideal candidate has a keen eye for UI execution, a proven "feel" for UX, and strong engineering fundamentals. You will translate complex management requirements into user‑friendly, responsive interfaces while building high‑performance APIs, robust bi‑directional integrations, and automated workflows.

Key Responsibilities

Frontend Architecture & UI Execution

• Develop, implement, and maintain robust, responsive, and intuitive web applications using ReactJS and TypeScript.
• Utilize Material Design libraries (MUI) to build a consistent, professional, and highly functional internal toolkit.
• Design and manage scalable design systems to ensure consistency across internal tooling projects.
• Optimize frontend performance and scalability, ensuring the interface remains 100% stable, intuitive, and high‑performing.

Backend Engineering & System Integration

• Develop and maintain robust server‑side logic (utilizing PHP/Symfony as our core platform language), ensuring high performance, responsiveness, and reliability.
• Design, implement, and document secure RESTful APIs and Web Services that adhere to industry standards.
• Build and maintain complex, bi‑directional data syncs across our enterprise stack (including Salesforce, NetSuite, Workday, and other custom internal tooling) to secure "One Source of Truth" across project data.
• Work with database systems, driving setup, maintenance, query optimization, and structuring.

Platform Evolution & Collaboration

• Evolve core platform features to meet adapting business needs, including time‑tracking modules, timesheet approval workflows, and advanced data validation.
• Integrate AI‑driven features like agentic workflows to automate internal processes and scale operational efficiency.
• Focus on reducing "gap time friction" and automating manual workflows to accelerate business velocity and eliminate operational bottlenecks.
• Debug, troubleshoot, and resolve complex full‑stack issues, bottlenecks, and performance bugs.
• Provide technical guidance, documentation, and support to the wider Monk community on the platform’s capabilities.

Qualifications

• Experience: 3‑5+ years of professional full‑stack web development experience.
• Frontend Expertise: Strong proficiency in ReactJS, with a solid foundation in TypeScript, JavaScript (ES6+), HTML5, and CSS3. Strong understanding of responsive design and cross‑browser compatibility.
• Backend Expertise: Strong backend development background. Experience with PHP and MVC frameworks (such as Symfony) is highly preferred; however, we are fully open to strong engineers from other language ecosystems who are willing to quickly adapt, leveraging AI‑assisted coding and development tools to bridge any syntax gaps.
• Integration & APIs: Proven experience in REST API design, Web Services, and integrating third‑party APIs (including authentication protocols like OAuth).
• Cloud & DevOps: Familiarity with modern cloud platforms (AWS, GCP, or Azure) and containerization/virtualization tools (e.g., Docker).
• Curiosity‑First Mindset: You don’t wait for a manual; you play, break things, and ask "What if?" to adopt new tools and workflows.
• Collaboration: Experience working effectively in agile development environments (Scrum/Kanban). Excellent communication and alignment skills.
• Language: Excellent communication skills in English, both written and verbal.

Technical Skills

• Frontend Tooling: Familiarity with modern frontend build tools and UI frameworks/libraries (e.g., TailwindCSS, Styled Components, Material UI, Vite).
• Testing: Experience with full‑stack testing practices and frameworks (e.g., Vitest, Jest, Playwright).
• Databases: Proficiency with database technologies such as SQL Server, PostgreSQL, or NoSQL databases.
• CI/CD & Infrastructure: Knowledge of DevOps practices, Git version control, and CI/CD pipelines.
• Security: Strong understanding of security principles and best practices in web application development (OWASP, data privacy, secure authentication).

Bonus Skills

• Experience with ERP and CRM integrations, specifically NetSuite and Salesforce.
• Familiarity with design tools such as Figma to facilitate developer‑to‑designer handoffs.
• Experience with container orchestration tools like Kubernetes.
• Experience or secondary proficiency in other programming languages (e.g., Node.js, Python).

#LI-Hybrid #LI-AS1

We are an equal‑opportunity employer committed to building a respectful and empowering work environment for all people to freely express themselves amongst colleagues who embrace diversity in all respects. Including fresh voices and unique points of view in all aspects of our business not only creates an environment where we can all grow and thrive but also increases our potential to produce work that better represents—and resonates with—the world around us.