Systems-minded product engineer with 20+ years of professional experience designing and delivering robust, scalable software.
I work primarily with Ruby and Rails, and have built and maintained systems in Go, TypeScript, and JavaScript. I’m currently deepening my work in Rust, drawn to its emphasis on correctness, safety, and performance. My background spans object-oriented design, microservices, and DevOps practices, with a focus on observability, security, and long-term maintainability. I bridge front- and back-end perspectives to align technical implementation with real product goals.
As a mentor, I help teams raise engineering standards through thoughtful code reviews, structured learning, and Lean principles that balance iteration speed with technical integrity. I integrate security and reliability into every design, believing that stable systems begin with disciplined thinking.
Senior Backend Software Engineer at Qonto
March 2022 – Present · Remote, freelance · Paris, France
Qonto is the leading European business finance solution, listed in the French Tech #Next40. It simplifies everything from everyday banking and financing to bookkeeping and spend management.
- Cards Platform: Improved transaction reliability and risk controls by refactoring authorization and settlement logic, enhancing chargeback detection, and adding clear customer notifications.
- Transaction Enrichment: Architected backend foundation enriching millions of transactions with merchant data, dual-write rollout, and Kafka-based publishing.
- Compliance & Market Expansion: Built scalable frameworks for ownership verification, AML screening, and regulatory data exchange — enabling smoother onboarding and support for multiple European markets.
- Engineering Standards: Contributed to company-wide API standards reducing friction between cross-functional teams. Acted as an internal Ruby mentor, designing and leading training sessions.
Microservices · Event-driven architecture · Distributed Systems · Ruby on Rails · Go · Kafka · Kubernetes · Prometheus · Grafana · Payments Infrastructure · KYC/KYB · AML Compliance
Senior Software Engineer at Shinrai
June 2021 – September 2021 · Contract · Budapest, Hungary
- Strengthened the Ruby test suite, improving reliability and preventing regressions.
- Refactored the core application initialization flow, reducing errors and simplifying system behavior.
- Containerized services to ensure consistent deployments and faster developer onboarding.
- Improved application security through codebase hardening and dependency updates.
Ruby · Rails · RSpec · Docker · Application Security · Software Architecture
Senior Software Engineer at Bitrise
December 2020 – June 2021 · Budapest, Hungary
Bitrise is a global mobile CI/CD platform serving customers from startups to Fortune 500s.
- Co-led Bitrise’s Ruby Task Force, improving engineering standards across multiple teams through targeted training, mentoring, and systematic code quality improvements.
- Delivered deep-dive sessions on Ruby/Rails performance, idiomatic patterns, ActiveRecord optimization, and testing strategies.
- Contributed across backend and frontend components (Ruby, Go, TypeScript, React), accelerating delivery on cross-functional projects during a critical scaling phase.
Ruby · Rails · Performance Optimization · Go · TypeScript · React · Technical Mentoring
Senior Ruby Developer at Emarsys
May 2019 – October 2020 · Budapest, Hungary
Emarsys is a global marketing automation platform (now part of SAP) used by thousands of businesses to drive customer engagement and revenue.
- Took ownership and led a major Rails framework upgrade within the first months, simplifying a large monolith and improving system reliability and developer productivity.
- Served as one of the main engineers of a core attribution product connecting purchases to marketing activity — a critical capability that helped clients sustain revenue during the pandemic.
- Raised engineering standards by teaching idiomatic, maintainable Ruby/Rails patterns and improving team understanding of core application behaviors.
Ruby · Rails · GCP · BigQuery · Legacy System Modernization · Performance Optimization · Technical Mentoring
Full-stack Freelancer
November 2014 – February 2020 · Budapest, Hungary
Worked as a full-stack consultant for clients across the UK and US, delivering end-to-end product development in Ruby/Rails and JavaScript. Helped teams ship faster, modernize legacy systems, and adopt maintainable engineering practices.
- Built and shipped full-stack features and products from initial architecture through deployment and maintenance.
- Modernized and stabilized legacy systems through refactoring, performance improvements, and clearer application structure.
- Provided Ruby/Rails training and hands-on guidance, helping teams adopt idiomatic patterns and improve code quality.
- Collaborated directly with founders and product teams, turning high-level requirements into clear technical plans and reliable delivery.
Software Architecture · API Design · Full-Stack Development · Ruby · Rails · JavaScript · Technical Consulting · Asynchronous Collaboration
Senior Software Developer at Shinrai
December 2017 – April 2019 · Budapest, Hungary
Shinrai is a Hungarian fintech company focused on cryptocurrency payment processing and digital asset services for businesses.
Co-authored a fully asynchronous, currency-agnostic background service in Ruby responsible for tracking, validating, and processing crypto assets across multiple exchanges. The system’s architecture — built around strict idempotence, self-correction, and rapid automatic recovery — delivered core business benefits:
- High reliability despite volatile exchange data.
- Accurate reconciliation of funds across volatile markets.
- Lower operational risk through automated recovery from network, API, or data integrity issues.
- Reduced manual intervention, enabling faster settlements and smoother exchange onboarding.
Cryptocurrency Infrastructure · Asynchronous Systems · Idempotent Design · Fault-Tolerant Architecture · Ruby · API Integration
JavaScript / Ruby on Rails Developer at TerraCycle
June 2014 – December 2014 · Budapest, Hungary
TerraCycle is an international upcycling and recycling company that collects difficult-to-recycle packaging and repurposes the material into new products.
- Joined as a front-end developer and quickly expanded into full-stack contributions on the next-generation global website using Ember.js.
- Improved frontend performance and maintainability by restructuring UI components and modernizing JavaScript code.
- Strengthened collaboration between frontend, backend, and product teams, reducing ambiguity and improving delivery speed.
JavaScript · Ember.js · Ruby on Rails · Frontend Development · Web Performance · API Design
Developer and Ruby/Rails Trainer at Unboxed
May 2009 – May 2014 · London, United Kingdom
Unboxed is a leading Ruby on Rails consultancy in London delivering digital products for government, public sector, and private-sector clients.
- Delivered multiple production Rails projects for government and enterprise clients, applying agile delivery to ship complex features on time and within budget.
- Served as a Ruby/Rails trainer for internal teams, UK universities, and major government organizations including the Ministry of Justice, Department for Work and Pensions, and Land Registry.
- Became a key advocate for knowledge sharing, establishing practices that improved code quality, collaboration, and engineering consistency across teams.
- Improved team productivity through code reviews, pair programming, and mentoring engineers in idiomatic Ruby, TDD, and maintainable system design.
Ruby · Rails · Agile · TDD · Technical Training · Pair Programming · Coaching & Mentoring
Web Developer at BeatThatQuote.com
March 2009 – May 2009 · London, United Kingdom
BeatThatQuote was a UK price-comparison platform for financial products, later acquired by Google.
- Delivered improvements to key user journeys and data integrations, ensuring accurate financial comparisons and smoother partner interactions.
- Refactored the JavaScript/AJAX layer to enhance frontend performance, reduce complexity, and make UI behavior more predictable.
- Migrated frontend code into a more modular, object-oriented structure, increasing maintainability.
JavaScript · Web Development · API Integration · UX · Code Refactoring
Web Developer at Last.fm
November 2007 – December 2008 · London, United Kingdom
Last.fm is one of the first music discovery services, providing personalised recommendations based on listening history.
- Worked on high-performance web services supporting 25M+ monthly users, gaining experience with large-scale traffic, caching strategies, and reliability.
- Served as lead developer for build.last.fm and the “Last.fm in a Box” platform, improving internal tooling and deployment workflows.
- Contributed to the public API, improving consistency and expanding functionality for third-party developers.
- Collaborated across teams to refine the custom PHP framework and strengthen core application behavior under heavy load.
High-Scale Web Applications · API Development · PHP · JavaScript
Web Developer at Webforce Ltd.
May 2006 – September 2007 · Budapest, Hungary
Webforce was a Budapest-based web development and hosting company. Here I played a pioneering role in introducing Ruby on Rails in Hungary — likely delivering one of the first fully deployed, production Rails applications in the country.
- Deployed one of Hungary’s earliest real-world Rails systems to production, demonstrating the framework’s viability.
- Introduced Ruby on Rails into the company’s toolkit, enabling faster development cycles and more maintainable codebases.
- Built and maintained web applications for SME clients, improving their online presence and operational workflows.
JavaScript · PHP · Ruby on Rails · Web Development · Linux
Front-end Developer at Carnation
2005 – 2006 · Budapest, Hungary
Carnation was a digital agency building marketing and web solutions for major brands. I focused on front-end development, delivering standards-compliant interfaces during an era of highly fragmented browser support.
- Built clean, cross-browser HTML/CSS interfaces that improved user experience and visual consistency across client projects.
- Helped streamline front-end delivery by introducing more structured markup and reusable styling patterns.
HTML · CSS · Frontend Development