Senior Full Stack (Blockchain) Engineer

Ciklum is looking for a Senior Full Stack (Blockchain) Engineer to join our team full-time in Poland. We are a custom product engineering company that supports both multinational organizations and scaling startups to solve their most complex business challenges. With a global team of over 4,000 highly skilled developers, consultants, analysts and product owners, we engineer technology that redefines industries and shapes the way people live. About the role: As a Senior Full Stack (Blockchain) 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 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 build robust, scalable backend services supporting high-volume on-chain transaction flows across multiple blockchain networks — both EVM and non-EVM Own end-to-end development of backend components and APIs — from architecture decisions to production deployment Lead integrations with DeFi protocols, on-chain data sources, and blockchain nodes across a wide range of chains and ecosystems Research and evaluate emerging blockchain technologies, protocols, and standards to keep Client platofrm at the cutting edge Optimize existing production systems for performance, reliability, and security — reducing latency and increasing throughput Collaborate closely with product, protocol research, and platform engineering teams to deliver high-quality solutions on time Drive features from inception through to delivery at scale, taking full ownership of the product lifecycle Work at the frontier of blockchain infrastructure, with real impact on how DeFi scales for institutional and retail users Tackle genuinely hard engineering problems — multi-chain routing, on-chain data indexing, protocol integrations, and more Collaborate with world-class engineers, protocol researchers, and product minds in a fast-growing global company Requirements: 5+ years of experience as a Backend or Full Stack Engineer Bachelor of Science ( B.Sc .) or equivalent degree/experience Blockchain and Web3 experience are a must — including deep understanding of transaction lifecycles, consensus mechanisms, smart contract interactions, and on-chain data Proven experience working across multiple blockchain ecosystems — EVM-compatible chains (Ethereum, Polygon, Arbitrum, Base, etc.) as well as non-EVM chains such as Solana, TON, Tron, or similar Proficiency in Node.js and TypeScript Experience designing and operating microservices in production CI/CD environments Strong understanding of security principles, cryptography, and best practices in a blockchain context Familiarity with DeFi protocols — AMMs, lending markets, bridging infrastructure, or on-chain routing — is a strong advantage Experience with Web3 tooling and libraries (ethers.js, viem, web3.js, Solana web3.js, etc.) Demonstrated experience taking products from inception to delivery at scale Full stack experience (React, frontend development) — a nice to have You think in systems and care deeply about correctness, reliability, and scale You’re comfortable navigating ambiguity and can drive technical decisions with limited oversight You have a natural curiosity for how blockchain protocols work under the hood — and you actually read the specs You thrive in fast-moving environments and can balance shipping velocity with long-term code quality You communicate clearly and collaborate effectively across engineering, product, and research Desirable: 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 What`s in it for you? 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 About us: At Ciklum, we are always exploring innovations, empowering each other to achieve more, and engineering solutions that matter. With us, you’ll work with cutting-edge technologies, contribute to impactful projects, and be part of a One Team culture that values collaboration and progress. With delivery centers in Wrocław and Gdańsk, our 300+ professionals in Poland drive forward-thinking solutions for global clients. Join a community where collaboration sparks innovation—and your impact reaches millions. Explore, empower, engineer with Ciklum! Interested already? We would love to get to know you! Submit your application. We can’t wait to see you at Ciklum. #LI-KZ1