**About the Role** Roles at Hugging Face are very fluid and dynamic -- we're looking for someone who is comfortable taking on different challenges that evolve over time. This role sits on the Xet Storage team, the group responsible for the storage system behind all of Hugging Face. Today we store over 200PB (and growing rapidly!) of the world's most important ML & AI assets. Xet is the underlying storage architecture for the entire Hugging Face platform and community -- from the largest model repositories to the datasets and Spaces that millions of people build on every day. In this role, you'll work across two closely connected surfaces. You'll contribute to xet-core, our open-source project written in Rust that powers hf-xet -- the Python library underpinning the Hugging Face Hub client and the wider ecosystem of open-source tools the community relies on. And you'll design, build, and operate meaningful and challenging features in the Xet Storage backend, contributing to the broader Infrastructure organization at Hugging Face. We're a small team building and operating incredible things at enormous scale, in a high-trust, low-process, async, and remote environment -- and we lean heavily on the latest AI tools to move fast. If you love writing low-level, high-performance code and are energized by the challenge of large-scale, scalable services, this is the team for you. This usually means proven experience building and operating production systems software, but we consider every applicant on an individual basis.

• Design, develop, and maintain scalable applications using Java • Lead by example and mentor a development team • Drive technical discussions and contribute to architecture decisions • Collaborate closely with stakeholders and cross-functional teams • Ensure clean, maintainable, and well-tested code • Take ownership of features and deliver end-to-end solutions independently

Role Description Ciklum is looking for an Expert JavaScript Engineer to join our team full-time in Poland. As an Expert JavaScript Engineer, become a part of a cross-functional development team engineering experiences of tomorrow. The world of digital assets is accelerating in speed, magnitude, and complexity, opening the door to new ways for leveraging the blockchain. Our Client’s platform and network provide the simplest and most secure way for companies to work with digital assets and it is trusted by some of the largest financial institutions, banks, globally-recognized brands, and Web3 companies in the world. The team continues to build and scale the infrastructure and developer tooling that has onboarded 50M+ wallets across crypto and fintech applications. In this context, the team powers the application-layer wallet experience and developer tooling, complementing core custody, security, and transaction infrastructure. The team operates with a strong product mindset and deep focus on security, reliability, scalability, and exceptional developer experience. Engineers build secure-by-default systems and approach their work with a strong customer focus, balancing technical excellence with real-world user needs. You will be joining a passionate group that moves fast, works with the biggest names in payments and fintech, and is defining how the next generation of financial applications are built. Responsibilities - Design and implement rich frontend experiences and scalable backend services that power Fireblocks’ wallet infrastructure through the Dynamic platform. - Own features across the stack: from technical design and architecture through implementation, testing, deployment, and ongoing optimization. - Build and maintain backend services and APIs supporting authentication, wallets, and payments infrastructure. - Develop user-facing features and frontend tooling for both end-user and developer-facing applications. - Collaborate closely with Product, Design, and other engineering teams to deliver robust, high-impact features. - Contribute to performance, reliability, and scalability improvements across the platform. - Help uphold engineering best practices through code reviews, testing, documentation, and knowledge sharing. Qualifications - 3–5 years of experience building and shipping production-grade, full-stack web applications. - Experience building backend systems and APIs using Node.js (and frameworks such as Express). - Comfort working across frontend and backend systems in complex, evolving codebases. - A strong appreciation for clean, maintainable code and system performance. - Experience collaborating cross-functionally with product and design partners. - Curiosity about fintech and Web3, and interest in building infrastructure used at global scale. Requirements - Experience with blockchain technologies (e.g., EVM chains, wallets, on-chain integrations). - Solidity experience – writing, deploying, testing, or interacting with smart contracts in production environments. - Experience maintaining, testing, and securing smart contract systems post-deployment. - Experience with a variety of state management solutions in production React applications. - Experience with security products or other high-sensitivity domains. Benefits - Strong community: Work alongside top professionals in a friendly, open-door environment. - Growth focus: Take on large-scale projects with a global impact and expand your expertise. - Tailored learning: Boost your skills with internal events (meetups, conferences, workshops), Udemy access, language courses, and company-paid certifications. - Endless opportunities: Explore diverse domains through internal mobility, finding the best fit to gain hands-on experience with cutting-edge technologies. - Flexibility: Enjoy flexibility – full remote working possibilities. - Care: We've got you covered with company-paid premium medical package through Luxmed. - Benefits: Access the MyBenefit cafeteria platform, allowing you to choose perks that best suit your lifestyle and needs.

• Design, develop, and maintain Python-based backend microservices • Build and integrate REST APIs (authentication, RBAC, third-party integrations) • Contribute to real-time voice pipeline integrations (SIP / WebRTC / LiveKit) • Develop integrations with external systems (e.g., Zoho CRM, Google / Microsoft Calendar) • Deploy and operate services on AWS (ECS, CloudWatch, Secrets Manager, S3) • Maintain CI/CD pipelines using Bitbucket Pipelines • Containerize services using Docker / Docker Compose • Collaborate with AI, front-end, and DevOps teams; participate in code reviews and release processes