Mission: Transform Nextcloud Office into a high-performance, modern web-based productivity suite, going beyond traditional DOM-driven applications. You will own the look and feel of the product, ensuring that even the most complex documents and spreadsheets remain fast, smooth, and responsive under heavy load. 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 Requirements: Technical 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 AI & Development Experience using AI-assisted development tools (e.g., Cursor or similar) Ability to use AI as a productivity multiplier without compromising code quality Profile Strong focus on smooth UI and rendering performance (60fps mindset) High level of English proficiency, with strong communication skills in an international team environment Attention to detail in user experience and visual quality Background in demanding frontend environments (e.g., interactive apps, data visualization, or graphics-heavy web applications) Pragmatic, execution-focused mindset What We Offer: Hybrid work model (with preference for our 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 Challenging frontend problems in high-performance environments Engineering culture focused on quality, performance, and continuous improvement