Andrii Saiak

Senior Backend / Blockchain Engineer | Stablecoins & Crypto Payments | Node.js · TypeScript · NestJS · Go · Solidity | C

Senior Backend Engineer / Blockchain Engineer · SokinKrakow, Poland

Joined Nov 2026

Backend engineer with 16+ years of commercial experience and 6+ years in blockchain and fintech. I design and build monolite and microservices, payment infrastructure and smart contracts, and integrate EVM and non-EVM networks into production systems. Comfortable owning architecture end to end: from API design and data modelling to Kubernetes deployments, monitoring and incident response. Former Tech Lead and Team Lead who mentors engineers, runs code reviews and works directly with product and business stakeholders. I use AI tools daily across the development cycle: AI-assisted coding and refactoring, code review, test generation, and faster debugging and root-cause analysis of production issues. Looking for a Senior / Lead Backend or Blockchain Architect role in a product company (fintech, payments, Web3, AI).

Experience

Senior Backend Engineer / Blockchain Engineer
Sokin
Dec 2025 - Present · 11 months · Full time
Architect and implement scalable blockchain infrastructure: transaction processing, wallet management and secure key handling. Build and maintain microservices for blockchain integrations: transaction broadcasting, balance tracking and event indexing. Design secure custody solutions, including key management flows, signing pipelines and risk mitigation strategies. Drive technical decisions and define architecture for blockchain products and services. Integrate stablecoin and crypto payment solutions into broader financial systems. Optimise transaction workflows and system performance across multiple chains. Stablecoins & cross-border payments.
BlockchainMicroservices
Senior Backend Engineer / Blockchain Architect
Kuna
Jan 2025 - Nov 2025 · 10 months · Remote
Architected and built Node.js/TypeScript microservices for a crypto payment platform. Designed the API and blockchain integration layer connecting EVM and non-EVM networks, with consistent transaction handling and data integrity across chains. Led technical direction for the product: architecture decisions, code reviews and alignment across teams. Owned production monitoring and reliability of high-load payment services.
Node.jsTypeScriptMicroservicesEthereumAPI DesignObservability