Zenon Jaskula

Architected and delivered features across a TypeScript monorepo, building React front ends, Node.js (Express, NestJS) services, and ETL pipelines for large volumes of event and transactional data. Designed and operated data-heavy analytical workloads using MongoDB, Redis, and Elasticsearch, implementing queue-based processing patterns and background job orchestration to ensure reliable, high-throughput delivery. Built event-driven microservices using Python (Django) and Java (Spring Boot) with Apache Kafka, and improved analytical query performance through GraphQL integration with Apollo. Contributed to zero-downtime CI/CD deployments using GitHub Actions, Jenkins, Docker, and Kubernetes. Implemented cloud-native AWS solutions (Lambda, ECS, RDS, S3, SageMaker) and improved availability while reducing costs. Delivered strong quality outcomes via unit, integration, snapshot, and end-to-end testing (Jest, Mocha, Cypress, React Testing Library, Selenium) and reduced production defects. Enh

Re-architected core platforms migrating from legacy AngularJS to React + Next.js SSR/SSG, improving SEO and reducing bounce rates. Built shopping cart and checkout microservices using Node.js, Redis, and Kafka, supporting real-time inventory sync, multi-currency, coupons, loyalty points, and tax/VAT logic. Integrated multiple payment gateways (Stripe, PayPal, Adyen, Braintree) with multi-gateway subscription billing, refunds, and dispute resolution using Java/Node/Python backends. Designed transaction analytics dashboards in React using GraphQL and Elasticsearch for real-time conversion and refund insights. Introduced event-driven architecture with Kafka and AWS SQS for payments, orders, and notifications. Automated CI/CD using GitHub Actions, Docker, and AWS CodePipeline with cloud-native infrastructure (AWS ECS, Lambda, DynamoDB, Kubernetes) to scale to 100K+ concurrent transactions. Supported quality through Storybook UI libraries, merge-request reviews, and end-to-end testing (Jest

Developed scalable eCommerce platforms using Shopify and Magento with React to improve conversions and reduce bounce rates. Migrated major legacy systems from PHP to MERN/MEAN (MongoDB, Express, React, Node.js / Angular), improving maintainability and reducing load times. Built CMS sites using Laravel, Symfony, and WordPress and integrated backend services with TypeScript components. Applied TDD with Jest, Jasmine, Cypress, and Karma to reach high code coverage and reduce QA cycles. Mentored junior developers and introduced coding standards to improve team productivity and consistency.