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.

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.

• 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 platform 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

• 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 life cycles, 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 Type Script
• 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, web
  3.js, Solana web
  3.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…