❗️ Important – On-Site Role in Poland, Warsaw❗️
⚡ We are looking for an experienced Senior HTML/Markup Developer to join our development team in Lisbon and help build and style high-quality iGaming websites. You will play a key role in crafting visually engaging and responsive interfaces by focusing on markup and CSS styling, turning Figma designs into fully functional, high-performance web experiences.

🎯 Your Mission:
Contribute to the creation and customization of new iGaming brand websites. You will be responsible for translating design specifications into pixel-perfect, responsive layouts while ensuring consistency, performance, and maintainability across multiple platforms. Collaboration with designers, developers, QA, and product teams will be central to your role.

✅ Responsibilities:
• Set up and customize new brand websites based on design specifications
• Implement and style interfaces following Figma layouts and branding guidelines
• Work closely with designers to fine-tune and resolve design nuances
• Customize and style key website components, including login and registration pages, dashboards, game halls, sports pages, and navigation elements
• Update and manage core framework versions across brands
• Ensure code quality through code reviews and release management
• Support live brands, handling styling updates, fixes, and feature rollouts
• Collaborate with cross-functional teams to deliver seamless user experiences
• Introduce creative ideas and contribute to continuous improvements in design implementation and performance

✅ Requirements:
• 5+ years of professional experience as an HTML/Markup Developer
• Excellent knowledge of HTML (Pug) and CSS (SCSS)
• Strong understanding of UI/UX design principles, responsive design, and cross-browser compatibility
• Proven experience building adaptive layouts and maintaining pixel-perfect visual quality across devices
• Solid knowledge of CSS/JS animations, transitions, and motion best practices
• Experience working with Figma / Sketch / Photoshop for translating design systems into production-ready interfaces
• Familiarity with CSS preprocessors (Sass/Less) and version control tools such as Git
• Understanding of web performance optimization and accessibility standards
• Strong collaboration skills with designers, QAs, and developers in multi-brand or large-scale environments
• Attention to detail, with an eye for visual precision and consistency
• Intermediate or higher level of English

✅ Nice to Have:
• Experience with frontend build tools (Gulp, Webpack, etc.)
• Knowledge of template engines (Pug, Handlebars, etc.)
• Experience working with CSS frameworks (Bootstrap, Tailwind, etc.)
• Understanding of HTML email templates
• Familiarity with Canvas API, WebGL, ThreeJS, or GSAP for advanced visual effects
• Basic knowledge of Angular (for integration purposes only)

✅ Recruitment Process:

1. Interview with the Recruiter: An introductory conversation to get to know you better, discuss your background, and align expectations about the role and the company.
2. Technical Assessment (HackerRank): A short coding challenge designed to evaluate your technical skills and problem-solving abilities.
3. Technical Interview: An in-depth discussion about your technical expertise, hands-on experience, and approach to solving real-world problems.
4. Final Interview with the Hiring Team: A conversation with team members and leadership to assess cultural fit, collaboration style, and alignment with the team’s goals.
5. Offer: If everything goes well, we’ll move forward with a formal offer to join our team.

About Shelf

The enterprise is going agentic — but most AI agents fail when they hit real business complexity. Shelf is changing that.

We’ve built the operating system for agentic AI: a platform that models your policies, workflows, and operational logic into an AI Data Model so agents don’t just respond — they reason. The result? AI that understands how your business actually runs and delivers precise, compliant, auditable outcomes at scale.

Brands like Amazon, Nespresso, HelloFresh, and KeyBank trust Shelf to power AI agents that resolve 85% of cases autonomously, cut handle times by 20–25%, and turn hours-long processes into seconds. We’re partnered with Microsoft, Salesforce, OpenAI, Snowflake, and Databricks — and recognized by Gartner (Cool Vendor) and IDC (Innovator) for our approach.

If you want to sell the infrastructure that makes agentic AI actually work in the enterprise, you’re in the right place.

Our mission is to empower humanity with better answers everywhere.

Senior Frontend React Developer:

As a Frontend Engineer at Shelf, you'll craft the interfaces that make enterprise AI accessible and trustworthy. While others are building chatbots, we're solving the harder problem: how do you build UIs that help users confidently navigate AI-powered systems processing millions of documents, while maintaining enterprise-grade reliability?

You won't just build React components — you'll architect production-ready Next.js applications that handle high-load scenarios with complex states, real-time AI streaming, and multiple layers of enterprise functionality. Every interface decision you make directly impacts how knowledge workers at the biggest companies in the market interact with their most critical information.

This is frontend engineering at its most demanding. You'll tackle challenges like building real-time streaming interfaces for LLM responses, architecting state management for concurrent AI operations across multiple tenants, creating accessible interfaces for complex knowledge graphs with thousands of nodes, and ensuring blazing fast interactions even with petabytes of searchable content. Your components will bridge everything from enterprise authentication systems to cutting-edge AI models, requiring both sophisticated technical skills and sharp product instincts.

We obsess over frontend quality because we're building the trust layer for AI itself. When your interfaces gracefully handle edge cases, provide clear feedback during AI processing, and remain performant under load, you're not just meeting UX standards - you're directly enabling users to trust AI-powered answers and make critical business decisions with confidence.

You'll work on production SSR applications serving thousands of enterprise users, implementing localization for global markets, ensuring accessibility compliance, and maintaining security standards that pass SOC 2 audits. Your code will integrate with our Elasticsearch clusters, DynamoDB tables, and Aurora PostgreSQL databases through the largest park of REST APIs, handling real-time websocket updates for AI streaming and collaborative features.

We're a product company that ships fast without compromising on lasting quality. You'll work alongside proactive, ever-learning engineers who actively use AI coding assistants (OpenAI Codex, Claude Code) to accelerate development. We build custom MCP servers, implement DSPy pipelines for LLM optimization, and experiment with different AI tools for implementation. In our environment, AI isn't just what we build — it's how we build.

The best engineers we know are drawn to problems that matter. If you're excited by the challenge of building interfaces that make the AI revolution actually usable and trustworthy for enterprise users, this role offers the rare combination of technical depth, meaningful impact, and the prestige of solving UX patterns that the industry hasn't figured out yet.

Responsibilities

• Design and implement production-ready Next.js SSR applications with complex state management, handling high-load scenarios and real-time AI interactions at scale
• Build interfaces for AI-powered features including streaming LLM responses, semantic search across millions of documents, interactive knowledge graphs, intelligent content recommendations, and AI agentic builders
• Architect component libraries and maintain our design system in Storybook, ensuring reusability, accessibility, and consistent UX patterns across the platform
• Develop enterprise-grade functionality including multi-language support, accessibility compliance, cross-browser compatibility, and security implementations that meet SOC 2 standards
• Create comprehensive technical specifications and component API designs that clearly communicate interface decisions, performance trade-offs, and accessibility considerations
• Build and optimize data-heavy UIs using React Flow for node-based graphs, Highcharts for analytics visualizations, and custom virtualization for handling large datasets
• Instrument components for performance monitoring, track Core Web Vitals, implement error boundaries, and build automated visual regression tests with Playwright
• Take full ownership of the features you build, monitoring their performance in production, optimizing bundle sizes, and ensuring they scale gracefully as user load grows
• Work with SWR for intelligent data fetching, caching, and revalidation strategies that minimize API calls while keeping UIs responsive and data fresh
• Integrate with backend services via REST APIs, handle websocket connections for real-time updates, and implement optimistic UI patterns for seamless user experiences
• Leverage AI coding assistants to accelerate development while maintaining high code quality, and contribute to building internal AI agents that automate frontend workflows
• Stay current with React ecosystem best practices, Next.js updates, AI UX patterns, and modern frontend architecture—experiment with new approaches and share findings with the team
• Contribute to our engineering standards and practices through thoughtful code reviews, mentor colleagues on frontend best practices, and actively participate in our culture of continuous learning

Requirements

• Over 5 years of professional frontend engineering experience, including more than 3 years specializing in React and modern JavaScript/TypeScript
• Production Next.js experience - you've built and shipped SSR applications at scale, understand app router patterns, server components, and the trade-offs between SSR, SSG, and CSR
• Deep TypeScript expertise - you write type-safe code with generics, utility types, and advanced patterns. 
• Complex state management - hands-on experience architecting state solutions for challenging scenarios: real-time collaboration, optimistic updates, multi-tenant data isolation, and large-scale data synchronization
• Enterprise application development - you've built applications with localization (i18n), accessibility, security best practices, and compliance requirements. You understand the complexity beyond "making it work"
• AI/LLM interface experience - you've built interfaces for AI-powered features: streaming token responses, chat UIs, semantic search, or similar real-time AI interactions
• High-load optimization - proven track record optimizing applications for performance under heavy traffic, large datasets, and concurrent operations. You monitor Core Web Vitals and know how to improve them
• Modern CSS mastery - strong expertise with Tailwind CSS and/or CSS-in-JS solutions. You can implement pixel-perfect designs while maintaining responsive layouts and dark mode support
• Write well-structured, testable code with thoughtful component abstractions and clean APIs. You know when to abstract and when to keep it simple
• Strong problem-solving skills and genuine curiosity - you don't wait for designs to be perfect but proactively identify UX issues and propose solutions. You're never satisfied with "good enough" and constantly refine your craft
• Experience with AI coding assistants (OpenAI Codex, Claude, etc.) and eagerness to push the boundaries of AI-assisted development. Part of this role involves creating AI agents to automate portions of the frontend workflow
• Familiarity with observability and monitoring tools like Datadog, Sentry, or similar platforms for tracking frontend performance and errors in production
• Upper-Intermediate or better English skills for technical communication, documentation, and collaborating with distributed teams
• Present your work effectively both verbally and visually - you can articulate design decisions, create component documentation, and explain technical trade-offs clearly

Be a Plus:

• Experience with React Flow, Highcharts, or other complex data visualization libraries
• Understanding of Node.js/Python/backend fundamentals - you can read backend code and contribute to API design discussions
• Experience with SWR, React Query, or similar data fetching libraries
• Hands-on experience with vector search UIs, RAG interfaces, or semantic search implementations
• Familiarity with MCP (Model Context Protocol), DSPy, or other cutting-edge AI frameworks
• Experience with monorepo tools (Lerna, Turborepo, Nx) and managing shared component libraries
• AWS services knowledge (S3, CloudFront, Lambda) and understanding of serverless architectures
• Built or contributed to design systems or open-source component libraries
• Experience with Playwright, Puppeteer, or Cypress for comprehensive E2E testing
• Experience building AI agent interfaces or agentic AI workflows

What Shelf Offers:

• B2B contract
• Company Stock Options
• Hardware: MacBook Pro
• Modern technical stack. Develop open-source software
• Premier AI development environment: GitHub Copilot, Claude Code, OpenAI Codex, TypingMind, v0, MCP Servers, plus credits for experimenting with emerging AI tools

Why Shelf

• Our Leadership Team has deep knowledge management and AI domain expertise and enterprise SaaS background to execute this plan
• We love our customers and our customers love us. Ask a Shelf customer why, and they’ll tell you it’s because of our innovative capabilities, rock-solid reliability, they truly enjoy working with our people, but most of all – it’s the improvements they see in their business KPIs.
• We have raised over $60 million in funding and our investors include Tiger Global, Insight Partners, Connecticut Innovations, and others
• We have high velocity growth powered by the most innovative product in our category, 3X growth for 3 years in a row
• We now have over 100 employees in multiple U.S. states and European countries, and we have ambitious hiring goals over the next few months

Our Values:

Quality - We’re united by our focus on world‑class Quality. Quality in all things – starting with everything that leaves your desk. Everything you touch – every email, report, campaign, and piece of code – should be outstanding. Your work product should blow people away. Having people look at what you’ve done and say, “Wow.” That’s the standard here. Remember that how you do anything is how you do everything. Focus on craftsmanship—your ability to make things better.

Momentum - for us means that you should know that the things you’re responsible for are moving forward. When you look around and see something that’s stalled, get it moving again. We pride ourselves on “ball movement.” When your boss or team leaves you with something, they should return to see measurable progress. Small, continuous movement is our recipe for success. Constantly look for how to make the work around you move forward. We want you to initiate solutions, ideas, and progress. Don’t wait for it to come to you—reach out and create movement. All the time.

Accountability - We expect every team member to feel that they are accountable for more than anyone might normally expect. Each of us should feel real responsibility for things even at the edge of our control. We consistently share and align on expectations, give each other open and respectful feedback, and use those two drivers to ensure that every agreement we make with one another is clear and complete.

Hard Work - We’re here to do something difficult together. We care intensely about the mission and we expect that from our teammates. That care means that we work hard here. Hard work comes with long hours, extra effort…and real opportunity at Shelf. Your passion for creating and sustaining output is a part of our DNA. Support each other, cheer each other on, drive the mission forward. Great teams sustain intense effort together to win.

Learning Agility - We’re innovating in one of the fastest‑moving spaces in history at a time of accelerating global change. That’s incredibly exciting and requires each of us to commit fully to learning each and every day so that we can be the best at what we do. None of us know everything. All of us can learn anything. Staying open and constantly curious is a key success driver at Shelf. It also requires humility. We prize people who are consistently humble and open to making mistakes and growing from them. Recognize also that learning itself is a skill…we need you to be really good at it. Keep dialing in your own understanding about how you learn best and push yourself to keep growing.

Adapt and Thrive - Overcoming challenges lives deep in our DNA. We have a proud history of understanding and living the reality that obstacles are our opportunities…they’re the key to our success. Change is a constant in our business and fighting change is counterproductive. We need you to be good at being uncomfortable and understand that discomfort is the key to growth. Cultivate your own ability to adapt and know that struggling well is something you’ll share with every team you’re on at Shelf. Our company stories are about thriving through real difficulty…together.

Win Together - We win or lose as a team. Always. Everything you do here is connected to the rest of the organization. Part of our shared team environment demands full honesty…real candor and directness with one another. We expect you to constantly be thinking about how to support your teammates and the company, always acting in service to our shared mission and what’s best for the organization as a whole.

We’re looking for a Full Stack Engineer to join the Documents Team. Our team is working on building and scaling a new web application, expanding the ecosystem of one of our key products. This is a great opportunity to have a real impact on product decisions, architecture, and user experience while working across both frontend and backend.

What you’ll do: 

• Developing user-facing application(s):

             - Main stack is Typescript, React, Nextjs, Tailwind

             - Back-end is Node, Nestjs, Postgres, AWS

• Back-end tasks to power new functionality for both web and iOS app
• Working with product and marketing teams to define clear requirements and estimates
• Writing tests
• Always teaching others and giving helpful feedback
• Good SEO and accessibility is a must
• Experience with various third-party integrations as we will integrate more and more

About you:

Front-end:

• React, CSS
• Next.js, TailwindSEO
• SEO, Accessibility
• Smooth animations
• Responsive UI
• Pixel-perfect implementation

Back-end:

• Nest.js and Postgres
• Distributed systems and event-based architecture
• SQL skills and experience working with ORMs
• CI/CD, and infrastructure setup
• Third-party integrations and their side-effects

Overall:

• Strong English skills (we have several required meetups in English, plus engineers present the features themselves in English)
• Enjoy working on pet projects, finds opportunities to learn and try something outside of work projects only
• Enjoy both back-end and front-end.

Would be a plus:

• AI integrations
• External LLM tools, like LangFuse, LangChain, etc.
• Desire to build automations
• Interest in knowledge sharing