Denys Z.

Engineering Lead and Solution Architect with over 18 years of experience in architecting, building and scaling enterprise systems, with deep expertise in payments, finance and accounting platforms and hands-on experience building AI-driven products (LLM agents, RAG, ML pipelines). I lead a team of around ten engineers, and at times two teams, and stay hands-on across the whole delivery cycle: shaping product requirements with product and business stakeholders, designing solutions, preparing plans and roadmaps, coding and maintaining production systems. I drive both strategic and tactical decisions across several domains while keeping systems reliable and scalable. I have a proven record of designing scalable, secure and efficient architectures: migrating legacy monoliths to microservices and event-driven systems, introducing cloud-native technologies and DevOps practices, and most recently onboarding engineering teams to AI-assisted development with a unified way of working that raised delivery throughput by 30-40% and cut maintenance time by up to 70%. Since 2025 I have also been designing and operating my own AI products end-to-end: an AI-powered trading platform (creatine.trade) and an AI real-estate deal-detection service covering LLM agents, retrieval-augmented generation, ML pipelines, event-driven architecture and production operations as a solo engineer. Technical & Architecture Experience: Full SDLC ownership: requirements analysis, system design, development, testing, deployment and maintenance. Architected Upwork's payment processing handling millions of transactions a year, integrating PSPs such as PayPal, Payoneer and Adyen plus cryptocurrency payments (BTC, ETH and others); secure, PCI-compliant design throughout. Led the move from a legacy Perl monolith to microservices and event-driven architecture, cutting complexity and improving scalability by ~30%; designed APIs that reduced invoice and reconciliation processing time by 25%. Delivered services automating settlement processing, reconciliations, bank-to-bank transfers and trading operations, with AWS and Docker-based deployment pipelines. Hands-on with data-driven and event-driven architectures that improve performance, scalability and communication between services.