CSS Jobs in Valencia.
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Frontend Engineer (Performance & UI Rendering)
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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
Ready to apply?
Apply to arsys EN
Medier isn’t just a marketing agency—we’re creative partners to our clients. From digital and social media strategies to PR, influencer collaborations, SEO, programmatic advertising, and CRM, we offer a comprehensive suite of expert services. By combining creativity with data-driven insights, we don’t just deliver campaigns—we deliver results.
Our philosophy is simple — hire a team of diverse, passionate people and foster a culture that empowers you to do your best work. Is it a match? You’re in.
Responsibilities:
- Code responsive HTML emails from scratch using table-based layouts and inline CSS
- Translate design mockups (Figma / Sketch) into production-ready email templates
- Ensure consistent rendering across 20+ email clients and environments — Gmail iOS and Android, Outlook 2013–2021, Apple Mail, Samsung Mail, Yahoo, and others
- Build and maintain a modular email template library
- Test emails thoroughly using Litmus or Email on Acid before every send
- Optimize images, handle retina/HiDPI assets, and manage fallbacks for unsupported CSS properties
- Write and manage media queries for mobile responsiveness
- Handle edge cases: dark mode support, web font fallbacks, Outlook conditional comments
- Implement dynamic content blocks using templating syntax (Liquid, AMPscript, or Handlebars) provided by the CRM team
- Maintain clean, commented, and well-documented code
Requirements:
- Expert knowledge of table-based HTML layout and inline CSS
- Strong understanding of how different email clients parse and render HTML/CSS
- Experience with Litmus, Email on Acid, or similar cross-client testing tools
- Solid grasp of responsive email techniques and mobile-first thinking
- Familiarity with dark mode rendering and how to handle it gracefully
- Experience with Outlook-specific hacks and conditional comments
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Ready to apply?
Apply to Medier
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