Arsys is a leading Spanish provider of cloud computing and web hosting services, managing over 1.5 million services for more than 260,000 clients. Founded in 1996, the company has established itself as a key player in the European digital infrastructure market, offering solutions ranging from domain registration to complex managed cloud environments. Headquartered in Logroño, Arsys maintains a strong presence across Spain with additional offices in Madrid and Barcelona. Since its acquisition by the United Internet Group (IONOS) in 2013, the company has integrated into a global network, making it an attractive destination for international tech talent seeking roles in system administration, software engineering, and cloud operations within a stable, established corporate environment.

Founded in 1996 in Logroño, Arsys became a pioneer in the Spanish internet market. In 2013, it was acquired by United Internet (IONOS), further expanding its reach and resources across Europe.

Frontend Engineer (Performance & UI Rendering)

Arsys

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We offer you the opportunity to join the leading Spanish company in the IT sector, with more than 25 years of experience and one of the most solid track records as a provider of technological solutions for companies.

We are a growing company with more than 400 employees and offices in Logroño, Madrid, Barcelona, Seville, Bilbao and Valencia.

Since August 2013, we have been part of the IONOS Group, Europe's leading digitalisation partner for small and medium-sized companies.

In short, we are a multicultural team that's passionate about technology, bringing our professional experience from over a dozen countries: Germany, Argentina, Spain, the United States, France, the Philippines, Italy, Poland, Portugal, the United Kingdom, Romania...

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