About the role

You will design and implement full-stack experiences for wallet infrastructure while owning features from architecture through deployment. You will also collaborate with cross-functional teams to build scalable backend services and user-facing frontend tools.

What they look for

JavaScript Node.js Express React Frontend development Backend development API development Full-stack development Blockchain Fintech Web3 Solidity Smart contracts System architecture Security Scalability

Requirements

Candidates must have 3–5 years of experience building production-grade full-stack applications with Node.js and frontend frameworks. A strong understanding of clean code, system performance, and an interest in fintech or Web3 infrastructure is required.

Benefits

Premium medical package MyBenefit cafeteria platform Internal events Udemy access Language courses Company-paid certifications Internal mobility Flexible working

Full description

Ciklum is looking for a Senior JavaScript 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 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 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

Requirements:

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

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.

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