Frontend Engineer - Performance & UI Rendering

6d6 days ago

Arsys

Valencia, ES · Full-time · €45,000 – €65,000

About this role

Join Arsys, the leading Spanish IT company with over 25 years of experience and part of IONOS Group, Europe's top digitalisation partner. As a growing team of more than 400 employees across multiple offices, we bring multicultural expertise from over a dozen countries. Your mission: transform Nextcloud Office into a high-performance, modern web-based productivity suite beyond traditional DOM-driven apps.

You will own the product's look and feel, ensuring complex documents and spreadsheets stay fast, smooth, and responsive under heavy load. Build advanced frontend features like charts, conditional formatting, and interactive elements using modern JavaScript. Deliver 60fps experiences in scrolling, typing, and zooming while shifting rendering to Canvas or hardware-accelerated tech.

Work in a passionate, multicultural team focused on technology and professional excellence. Collaborate across offices in Logroño, Madrid, Barcelona, Seville, Bilbao, and Valencia. Leverage AI tools to boost development without sacrificing performance or UI quality.

Enjoy a hybrid work model with flexible hours and locations like Alcobendas or Valencia. Benefit from personalized training, biannual events, and unrestricted access to advanced AI tools. Thrive in an engineering culture emphasizing quality, performance, and continuous improvement.

Requirements

Strong experience with modern JavaScript (ESNext)
Deep understanding of DOM behavior and performance trade-offs
Experience with Canvas API or rendering libraries (e.g., PixiJS or Fabric.js)
Solid knowledge of frontend performance optimization techniques
Experience using Web Workers to offload work from the main thread
Experience with modern CSS and performance-oriented styling
Experience using AI-assisted development tools (e.g., Cursor or similar)
Strong focus on smooth UI and rendering performance (60fps mindset)

Responsibilities

Build new frontend features such as advanced charts, conditional formatting, and interactive document elements
Develop fast, responsive user interfaces using modern JavaScript
Ensure a smooth 60fps experience across all user interactions (scrolling, typing, zooming)
Move performance-critical rendering logic from the DOM to Canvas or hardware-accelerated technologies
Refactor legacy styles into a modern, performance-optimized CSS system based on variables (supporting dark mode and high-contrast themes)
Implement responsive UI patterns such as optimistic UI to improve perceived performance
Collaborate with other teams to optimize latency and real-time user experience
Leverage AI tools to accelerate development while focusing on performance, edge cases, and UI quality

Benefits

Hybrid work model (preference for offices in Alcobendas, Valencia, Barcelona, Sevilla, or Logroño)
Flexible working hours
Flexible compensation package
Discounts on Arsys products
Discounts on technology brands
Personalized training and development plans
Biannual team events
Access to advanced AI tools with no usage restrictions