Bartłomiej is available for hire
Hire BartłomiejBartłomiej Łoza
Verified Expert in Engineering
Full-stack Developer
Warsaw, Poland
Toptal member since July 27, 2020
Bio
Bart is a seasoned full-stack JavaScript developer with over a decade of hands-on experience using a variety of frameworks (Redux, Angular, AngularJS, and React Native), and libraries (React, Node.js, and Vue.js). Bart has a wide range of experience working as a senior developer and team leader for major corporations like Lufthansa, ERGO, and IGT (formerly Gtech), PZU, PLAY, and Danske Bank and also for US-based startups, SOCI and LabFellows.
Portfolio
Danske Bank
Node.js, Redux-Saga, Jest, Cypress, TypeScript, GraphQL, Redux, Java...
Endeavor
JavaScript, React, Next.js, Tailwind CSS, Node.js, TypeScript, GraphQL...
SOCI, Inc.
Backbone.js, Responsive Web Design (RWD), jQuery, HTML5, CSS3, JavaScript
Experience
Availability
Full-time
Preferred Environment
Jira, Slack, GitHub, Chrome, Visual Studio Code (VS Code), MacOS
The most amazing...
...project I've implemented was a Mapbox-based app for a real estate broker where I led a 4-person team in order to develop an E2E project in three months.
Work Experience
Team Lead
2019 - PRESENT
Danske Bank
- Prepared and implemented an optimal architecture for a system that has been operating for several years.
- Prepared a concept of a shared component library based on React, Storybook, and styled-components.
- Implemented, in barely two months and under a very tight deadline, a critical module for a huge Danske Bank mobile application.
Technologies: Node.js, Redux-Saga, Jest, Cypress, TypeScript, GraphQL, Redux, Java, React Native, React, Architecture, Single-page Applications (SPA), Next.js, WordPress, Search Engine Optimization (SEO), Vercel
Full-stack Software Engineer
2022 - 2024
Endeavor
- Played a pivotal role in defining and executing tasks, drawing on business requirements to guide development. This involved integrating third-party software for enhanced marketing and notification capabilities.
- Implemented several key features that enhanced user experience, such as advanced permission settings and interactive poll functionalities.
- Managed the application release process efficiently, ensuring smooth and timely deployments.
- Extended my expertise beyond traditional coding. Actively engaged in both front-end and back-end development, ensuring seamless integration and functionality.
- Contributed to the DevOps aspects of the project, gaining valuable experience in this area.
Technologies: JavaScript, React, Next.js, Tailwind CSS, Node.js, TypeScript, GraphQL, Playwright, GitHub Actions, PostgreSQL, NestJS
Lead Front-end Engineer
2019 - 2019
SOCI, Inc.
- Migrated a project from ES5 to the ES6+ JavaScript version.
- Implemented a fully responsive mobile version of the application.
- Introduced ES6+ features during internal workshops for other employees.
Technologies: Backbone.js, Responsive Web Design (RWD), jQuery, HTML5, CSS3, JavaScript
Team Lead
2018 - 2019
LabFellows
- Designed a new architecture concept, mainly related to performance optimization, state management, and API facade.
- Introduced newest React concepts to the front-end team like React Hooks, Portal API, mainly based on my knowledge gained during ReactiveConf in Prague.
- Prepared a refactoring roadmap (instructions on how to deal with the old code, chunk by chunk).
- Supported, educated, and prepared dedicated workshops for younger members of the front-end team.
- Rearchitected contracts between the front end (FE) and back end (BE) made together with the back-end team leader.
- Prepared ESLint, prettier configurations, and introduced pre-commit hooks.
Technologies: Styled-components, Webpack 4, Material UI, Jest, Cypress, Redux, React, ECMAScript (ES6)
Full-stack Developer
2018 - 2018
Lufthansa Innovation Hub
- Implemented an itinerary React Native MVP app from scratch.
- Designed data models and contracts between the front end and back end.
- Implemented new screens and flows which were based in the US and wireframes prepared carefully in advance by our BAs and designers.
Technologies: Enzyme, Jest, Android Studio, Xcode, Redux, React Native, ECMAScript (ES6)
Full-stack Developer
2017 - 2018
Ergo Digital IT
- Refactored a React application in order to use best practices.
- Implemented Node.js microservice for PDF generation purposes.
- Introduced a Redux state management architecture concept.
Technologies: Docker, Webpack, Express.js, Jest, PostgreSQL, Node.js, Redux, React
Full-stack Developer
2016 - 2017
IGT (formerly Gtech)
- Developed a back-office AngularJS-based application with a strong focus on charts.
- Refactored an Angular-based application to Redux architecture.
- Adjusted and deployed a stable version of the lottery CRM app in North Carolina (US).
Technologies: Protractor, Chai, Karma, Jasmine, Node.js, Docker, Flexbox, Webpack, Redux, Angular, AngularJS, ECMAScript (ES6)
Senior Front-end Developer
2016 - 2016
PZU
- Developed a directed self-service application for individual customers.
- Implemented web designs in order to support even IE6.
- Introduced Angular concepts during internal workshops.
Technologies: CSS3, HTML5, BEM, Sass, XSLT, Backbone.js, Angular
Full-stack Developer
2014 - 2016
PLAY
- Designed and implemented Flux-like, component-based architecture on top of AngularJS with the addition of Highcharts.
- Designed and developed a series of highly configurable offer form controls.
- Implemented a communication system between the CRM and embedded applications.
Technologies: Highcharts, Node.js, CSS3, HTML5, jQuery, JavaScript, Grunt, Gulp, AngularJS
Full-stack Developer
2014 - 2015
AUTOMATUM
- Designed and implemented a single-page application (SPA) with multiple dynamic forms.
- Implemented mechanisms that made clients' data anonymous for certain system users (privileges system).
- Implemented algorithms prepared by a financial analyst.
Technologies: CSS, HTML, JavaScript, React
System Architect | Full-stack Developer
2012 - 2015
TTG Events
- Designed and implemented the architecture of the internal CRM system.
- Implemented algorithms used for matching potential clients with tourism agencies.
- Implemented a React-based internal application and WordPress widget used for the registration of potential customers.
Technologies: jQuery, React, JavaScript, CSS, HTML, MySQL, PHP
Junior PHP/JavaScript Developer
2012 - 2013
Kompan.pl
- Wrote the documentation and took care of the maintenance of an internal CRM application based on the Symfony-like PHP framework.
- Implemented a procurement module for a culinary school.
- Implemented modules (private messages, friends network, and user preferences) for a social network application.
Technologies: jQuery, CSS, HTML, JavaScript, Symfony, PHP
Junior Front-end Developer
2009 - 2012
Freelance Work
- Implemented landing pages based on designs prepared in Photoshop.
- Adjusted WordPress themes according to client requirements.
- Prepared the HTML and CSS layers of the pages based on the designs.
Technologies: jQuery, HTML, CSS, JavaScript
Experience
PZU Self Service App
The project involved a PZU self-service application.
I was a front-end developer. My role was to create a pixel-perfect implementation of the design and flows based on user stories prepared by BAs and designers. The application was Angular based along with some Backbone.js and XSLT transformations.
I was a front-end developer. My role was to create a pixel-perfect implementation of the design and flows based on user stories prepared by BAs and designers. The application was Angular based along with some Backbone.js and XSLT transformations.
eCommerce Admin Panel
This project involved building an eCommerce application from scratch.
I was the team leader of a distributed front-end team responsible for implementing the admin panel from scratch. It was a challenging project because my team consisted of six front-end developers, and my role was to architect the app and implement new features as well as coordinating the whole team so that we made progress in the correct direction. I also prepared the backlog and user stories based on the designs delivered in advance.
I was the team leader of a distributed front-end team responsible for implementing the admin panel from scratch. It was a challenging project because my team consisted of six front-end developers, and my role was to architect the app and implement new features as well as coordinating the whole team so that we made progress in the correct direction. I also prepared the backlog and user stories based on the designs delivered in advance.
eProcurement Platform for Science
LabFellows.com is a platform for science.
I was the team leader of the front-end team who joined the project at a very critical moment. On one hand, my role was to refactor the React codebase because it had very big technical debt and on the other, I was also guiding two front-end developers in the implementation. The application was implemented in React without any state management system or even tests.
My Implementation Tasks:
• Redux State Management
• E2E Tests in Cypress
• Jest Unit Tests
• Proper ESLint and a Prettier Configuration
• React Hooks
I was the team leader of the front-end team who joined the project at a very critical moment. On one hand, my role was to refactor the React codebase because it had very big technical debt and on the other, I was also guiding two front-end developers in the implementation. The application was implemented in React without any state management system or even tests.
My Implementation Tasks:
• Redux State Management
• E2E Tests in Cypress
• Jest Unit Tests
• Proper ESLint and a Prettier Configuration
• React Hooks
Education
2009 - 2014
Master of Engineering Degree in Computer Science
Warsaw University of Technology - Warsaw, Poland
Certifications
OCTOBER 2019 - PRESENT
Psychology of Emotions Part 2
Starway Institute
SEPTEMBER 2019 - PRESENT
Auditing Security and Protecting Web Applications
IT Security: Audits & Trainings (Niebezpiecznik.pl)
JULY 2019 - PRESENT
NLP 2
Starway Institute
JUNE 2019 - PRESENT
Psychology of HR
STARWAY Institute
MAY 2019 - PRESENT
Psychology of Sales
STARWAY Institute
MAY 2019 - PRESENT
NLP 1
Starway Institute
APRIL 2019 - PRESENT
Agile Leadership — Management 3.0
Management 3.0 (Management30.com)
APRIL 2019 - PRESENT
Psychology of Marketing
Starway Institute
MARCH 2019 - PRESENT
Psychology of Emotions Part 1
Starway Institute
FEBRUARY 2019 - PRESENT
Psychology of Management
Starway Institute
AUGUST 2017 - PRESENT
Angular 2 Space
Tomasz Borowski
Skills
Libraries/APIs
React, REST APIs, Node.js, Vue, jQuery, Highcharts, Flexbox, Chai, Backbone.js, Redux-Saga, Playwright
Tools
Git, GitHub, Slack, Jira, Gulp, Grunt, Webpack, Karma, Xcode, Android Studio, Webpack 4
Languages
JavaScript, CSS, GraphQL, TypeScript, HTML, PHP, HTML5, CSS3, ECMAScript (ES6), Java, XSLT, Sass
Frameworks
Redux, Next.js, Angular, AngularJS, React Native, Chrome, Symfony, Jasmine, Protractor, Jest, Express.js, Cypress, Material UI, Tailwind CSS, NestJS
Paradigms
Search Engine Optimization (SEO), Responsive Web Design (RWD), BEM
Platforms
WordPress, Vercel, Mapbox, MacOS, Visual Studio Code (VS Code), Docker
Storage
MongoDB, MySQL, PostgreSQL
Other
Single-page Applications (SPA), Architecture, Enzyme, Styled-components, GitHub Actions
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