Jacek Z.

Jacek worked on a large-scale healthcare platform, improving backend functionality, system quality, and engineering reliability. A significant part of his work focused on identifying performance bottlenecks, optimizing database queries, and improving indexing strategies to enhance system responsiveness and scalability. He also collaborated closely with developers and QA to review pull requests, strengthen testing practices, refine release processes, and resolve production issues, contributing to safer deployments and higher overall quality standards.

Jacek worked on a WordPress-based web project for a hospitality SaaS company, balancing technical quality with measurable business impact. He partnered closely with the marketing team to implement campaign tracking, analytics integrations, and website changes supporting paid acquisition and conversion goals. At the same time, he improved website performance and front-end efficiency to enhance load speed, reliability, and overall user experience.

• Participated in the development of an eCommerce platform, creating new functionalities using PHP and JavaScript.
• Transitioned to rebuilding the platform with React.js and Next.js to improve performance and user experience.

• Served as Lead Backend Developer for a US-based startup focused on helping people fall asleep.
• Managed the backend of a mobile application that allowed users to join live sleep sessions with a guide to help them relax and fall asleep.
• Built functionality to serve live stream URLs from AWS and handle video transcoding after each session.
• Developed a CMS for managing sleep sessions and user accounts.

• Developed a web application that allowed users to record video testimonials.
• Designed and implemented major new features for an internal CMS.

• Fully coded Jakdolece.pl, a start-up offering unbeatable travel deals for flights and hotels worldwide, from frontend to backend.
• Leveraged data analysis to ensure the platform continuously updated with the most affordable prices, keeping all offers competitive around the clock.

• Led a team of programmers.
• Planned implementation schedules and prioritized tasks.
• Developed solution designs and architecture.
• Built and maintained Manufacturing Execution System (MES) and Enterprise Resource Planning (ERP) systems.
• Maintained traceability and tracking throughout the manufacturing process.
• Built and improved REST APIs.

His main tasks included PHP5 (Drupal 7), Python (Django) and frontend development (HTML5, CSS3, jQuery).

Building web applications - PHP5 object-oriented programming.