Matas K.

Senior Full Stack Engineer

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Visaginas, Lithuania

Experience

Sep 2024 - Present
1 year 4 months
Zürich, Switzerland

Senior Full Stack Engineer

Farmy

  • Architected and implemented Java Spring Boot microservices for order management and inventory synchronization, reducing stock-out incidents by 20% through event-driven Kafka pipelines.
  • Built React frontends with Hooks and Redux Toolkit, improving UI responsiveness for 50k+ monthly active users.
  • Introduced AI-driven dynamic pricing engine (Python ML services integrated with Java APIs), increasing gross margin by 8%.
  • Migrated critical modules to AWS EKS + Terraform, ensuring scalability during peak demand and achieving 99.95% uptime.
  • Implemented CI/CD pipelines with GitHub Actions and Docker, cutting release cycles from 2 weeks to 3 days.
  • Designed GraphQL APIs for mobile app integrations, supporting customer and vendor-facing applications.
  • Applied hexagonal architecture principles to decouple domain logic from infrastructure, improving testability and maintainability.
  • Enhanced caching strategies with Redis and database optimization in PostgreSQL, reducing checkout API latency by 30%.
  • Developed blockchain prototype for farm-to-table traceability, enabling transparent product origin tracking.
  • Mentored junior engineers on Java microservices, React optimization, and cloud-native best practices, improving team delivery velocity by 15%
Nov 2020 - Sep 2023
2 years 11 months
Prague, Czech Republic

Full Stack Engineer

Mews

  • Developed Java Spring Boot reservation and billing services, processing 1M+ monthly transactions across hotels and hostels.
  • Built React dashboards for hospitality managers with real-time booking visualization, improving operational decision-making speed.
  • Integrated AI-powered demand forecasting models into the booking pipeline, reducing overbooking incidents by 12%.
  • Migrated monolith modules to Kubernetes-based microservices with CI/CD automation, increasing release frequency by 40%.
  • Designed and exposed REST/GraphQL APIs to third-party booking providers, enabling faster onboarding of B2B integrations.
  • Improved payment flow by implementing blockchain-based smart contracts for secure deposits, reducing disputes.
  • Applied CQRS and event sourcing patterns for financial transactions, improving auditability and system reliability.
  • Automated testing (JUnit, Jest, Cypress) and monitoring (Datadog, ELK Stack), reducing production issues by 25%.
  • Refactored legacy AngularJS modules to React with TypeScript, cutting frontend technical debt.
  • Mentored cross-functional teams on clean architecture and API-first design, improving collaboration across frontend, backend, and DevOps.
Feb 2018 - Oct 2020
2 years 9 months
Kaunas, Lithuania

Full Stack Developer

Sanitas

  • Built Java Spring Boot APIs for patient records and prescription tracking, ensuring compliance with healthcare data regulations.
  • Designed Angular dashboards for doctors and pharmacists, enabling real-time access to medical histories.
  • Integrated AI-based symptom checker module (Python NLP with Java APIs), reducing unnecessary clinic visits by 10%.
  • Deployed services to Azure Kubernetes Service (AKS), improving scalability for regional hospital networks.
  • Developed blockchain-based prototype for prescription authenticity validation, reducing fraud risk.
  • Implemented CI/CD pipelines with Jenkins and Docker, reducing deployment errors by 35%.
  • Optimized Hibernate queries and applied Redis caching, improving patient data retrieval by 25%.
  • Collaborated with mobile team to design backend APIs for Android/iOS apps, ensuring consistent data access.
  • Conducted unit and integration testing with JUnit, Mockito, and Selenium, raising automated coverage to 85%.
  • Applied DDD (Domain-Driven Design) for healthcare modules, simplifying future enhancements and integrations.
Jul 2016 - Feb 2018
1 year 8 months
Kaunas, Lithuania

Web Developer

TeleSoftas

  • Developed Java-based backend modules and AngularJS/React frontends for client-facing projects across finance and logistics.
  • Implemented microservices for invoice management using Spring Boot and REST APIs, streamlining processing for enterprise clients.
  • Built React dashboards with Redux for delivery tracking systems, improving user satisfaction scores by 15%.
  • Assisted in deploying applications to AWS (EC2, RDS, S3) with Docker-based workflows, ensuring 99% uptime.
  • Introduced AI-driven OCR module for document scanning and invoice recognition, reducing manual data entry by 30%.
  • Implemented CI/CD pipelines with Jenkins, enabling continuous deployments and faster delivery to clients.
  • Improved performance by optimizing SQL queries and implementing Redis caching layers.
  • Collaborated with mobile developers to design backend APIs for cross-platform applications.
  • Wrote automated tests with JUnit, Selenium, and Jest, improving release reliability.
  • Participated in architectural reviews, contributing to decisions on migrating legacy systems to modern Java + React stacks.

Summary

Senior Full Stack Developer with 8+ years of experience designing and delivering high-performance applications using Java (Spring Boot, Hibernate) and React/Angular. Proven track record in building cloud-native, microservices-based architectures across SaaS, healthcare, hospitality, and e-commerce domains. Skilled in integrating AI/ML-driven modules, optimizing system scalability through DevOps automation (CI/CD, Kubernetes, Terraform), and applying architectural concepts such as hexagonal architecture for maintainability. Adept at mentoring teams, implementing blockchain-based modules for secure transactions, and consistently delivering measurable improvements in system performance, user engagement, and business outcomes.

Skills

  • Backend: Java (Spring Boot, Hibernate, Jpa), Rest Apis, Graphql, Microservices, Event-driven Systems
  • Frontend: React (Hooks, Redux, React Query), Angular, Typescript, Javascript, Css/scss
  • Ai & Emerging Tech: Ai/ml (Python Nlp, Tensorflow, Forecasting Models), Blockchain (Smart Contracts, Traceability, Authentication)
  • Cloud & Devops: Aws (Eks, Lambda, Rds, S3), Azure, Docker, Kubernetes, Terraform, Jenkins, Github Actions, Gitlab Ci/cd
  • Architecture: Hexagonal, Ddd, Cqrs, Event Sourcing, Api-first Design, Clean Architecture
  • Testing & Monitoring: Junit, Jest, Cypress, Selenium, Mockito, Datadog, Elk, Prometheus
  • Databases & Caching: Postgresql, Mysql, Mongodb, Redis

Languages

English
Advanced
Lithuanian
Advanced
Czech
Elementary
German
Elementary

Education

Oct 2012 - Jun 2016

Kaunas University of Technology

Bachelor of Science, Informatics · Informatics · Kaunas, Lithuania

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