Krzysztof – React, Golang, JavaScript

A hyperlocal on-demand delivery platform that connects customers with local restaurants, grocery stores, and retail businesses. It provides convenient access to a wide range of products through fast, reliable delivery at competitive prices, helping local businesses reach more customers and expand their sales.

• Contributed to a production microservice serving 100% of checkout page views and handling order placement.
• Worked across Golang, Ruby, Typescript, and React on the Consumer Checkout experience.
• Led delivery of a new cross-platform Consumer Checkout and contributed significant backend and web code for a high-volume production system.
• Led projects involving cross-team and cross-company collaboration, including meal-card integration and checkout initiatives.
• Investigated complex production bugs on critical code paths where defects could cause significant incidents or financial impact.
• Coordinated multiple streams of work, unblocked engineers, and helped align teams on delivery plans.
• Set up monitoring dashboards to verify deployments and identify production issues quickly.
• Created 1,000+ pull requests during the engagement.

Collaborative, web-based platform for scientific writing and research publishing. It enables researchers, academics, and scientific teams to create, edit, organize, and share research documents, manage references, and collaborate on manuscripts in real time. The platform supports academic publishing workflows and helps streamline the preparation of scientific papers for publication.

• Modernised a mature Ruby and JavaScript codebase and kept dependencies up to date.
• Fixed hundreds of bugs and simplified the codebase while improving maintainability.
• Improved performance through caching, reducing operations, reducing JavaScript bundle size, and deferring scripts.
• Created new functionality including scientific-paper peer review and DOI versioning.

Community-driven music and event platform that connects independent artists, event organizers, music enthusiasts, and sponsors. It provides tools for music streaming, event ticketing, memberships, and artist-curated content, helping creators reach global audiences, generate revenue, and preserve cultural and musical heritage.

• Improved site speed.
• Implemented search for events, users, and organisations.
• Fixed bugs and improved SEO.

AI-powered sales operations platform that helps businesses manage and optimize their sales funnels, from lead acquisition to booked sales calls. It combines automated appointment scheduling, AI-driven lead scoring, prospect nurturing, and sales analytics to improve lead quality, increase call attendance, and maximize sales conversion rates.

• Developed React/ES6 frontend and Ruby on Rails backend applications.
• Optimised Webpack configuration, bundle size, and code splitting.
• Integrated Twilio, Stripe, and Pipedrive webhooks.
• Delivered new features, backend KPI functionality, and extensive refactoring.

A software development and e-commerce engineering company specializing in custom online stores, B2B e-commerce platforms, and multi-vendor marketplaces. The company also leads the development of Spree Commerce, an open-source e-commerce platform that enables businesses to create flexible, scalable online shopping experiences, integrate third-party services, and streamline digital commerce operations.

• Built and launched e-commerce projects using Ruby on Rails, React, and ElasticSearch.
• Implemented server-side rendering, product search, indexing, and filtering across multiple projects.
• Solved complex production bugs and helped coordinate development teams.
• Mentored junior developers and acted as a technical/team lead.