Agata Andrzejewska, Developer in Copenhagen, Denmark
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Agata Andrzejewska

Verified Expert  in Engineering

Front-end Developer

Copenhagen, Denmark
Toptal Member Since
September 18, 2017

Agata is a full-stack web app developer with an academic background in computer science and a great interest in algorithms and mathematics. She is passionate about learning and enjoys challenges. She has successfully worked on multiple projects, from designing apps from scratch, implementing secure solutions, improving app performance, taking care of the best UX, and writing clear testable code.


React, TypeScript, ECMAScript (ES6), SCSS, React Redux, Design...
Secureframe, Inc
React, JavaScript, Front-end, TypeScript, GraphQL, Storybook, Code Architecture...
React, Node.js, Hapi.js, PostgreSQL, Amazon Web Services (AWS), Docker, SCSS...




Preferred Environment

Git, Linux, MacOS, Visual Studio Code (VS Code)

The most amazing...

...project I was involved in used mathematical statistics, cryptography, and network protocols to send encrypted steganography messages during a VoIP call.

Work Experience

Senior Front-end Developer

2021 - 2023
  • Built an internal platform in React and TypeScript for organizing events. It is intended to be used by more than 20,000 users.
  • Designed and implemented components for managing app functionalities, adding participants to actions, adding and editing applications, listing bulk actions, and generating PDF documents.
  • Added CSS styles to the whole app to be beautiful, easy to navigate, and accessible.
  • Connected the app with API in Python Django. Worked with the back-end team to make the app safe.
Technologies: React, TypeScript, ECMAScript (ES6), SCSS, React Redux, Design, Web Accessibility, Code Architecture, Web Development, HTML5, Cypress

React Front-end Engineer

2021 - 2022
Secureframe, Inc
  • Implemented new components with React and TypeScript for an existing app.
  • Created pixel-perfect reusable components based on Figma designs with TypeScript and CSS.
  • Collaborated with a team to quickly include the clients' feedback and make the app intuitive and easy to navigate.
Technologies: React, JavaScript, Front-end, TypeScript, GraphQL, Storybook, Code Architecture, Full-stack, HTML5, Figma, Pixel Perfect, Responsive Web Apps

Senior Full-stack Developer

2019 - 2020
  • Rebuilt an existing app from MVP to a secure version with fully developed planned functionalities.
  • Planned and executed all the processes needed to launch and maintain the app.
  • Designed and implemented the application's front-end architecture with React, Redux, and JavaScript.
  • Designed and implemented the application's back-end architecture with hapi.js and PostgreSQL database.
  • Designed and built a hierarchical comment system for a social app focused on performance and a good UX.
  • Added tests on the back end, reaching 80% coverage.
  • Fixed security issues on the back end and front end.
Technologies: React, Node.js, Hapi.js, PostgreSQL, Amazon Web Services (AWS), Docker, SCSS, Code Architecture, Full-stack Development, Full-stack

Full-stack Developer

2018 - 2019 (Open-source Volounteering)
  • Migrated an app from AngularJS to React, a work in progress.
  • Adjusted the look of the app using Bootstrap and Sass.
  • Reviewed the code and supported other contributors with React knowledge.
Technologies: AngularJS, Express.js, Node.js, Bootstrap, React, Web Development

Co-founder | Developer

2017 - 2019
  • Designed and built parts for additional functionalities in a REST API using Express.js and Node.js.
  • Refactorized part of the validating process on the Node.js/Express.js query path by implementing a parser used as one of the pieces of the middleware software.
  • Designed and implemented REST API responses for various queries using Node.js and ArangoDB Query Language.
  • Added JWT validation to increase the security of the users.
Technologies: JavaScript, ArangoDB, Angular, Express.js, Node.js, Web Development, Full-stack, HTML5

Full-stack Developer

2017 - 2018
  • Designed and built multiple REST API microservices using Express.js and Node.js.
  • Engineered and added JWT validation and fixed bugs with security.
  • Pioneered and wrote SQL queries generator for MySQL database.
  • Created detailed tests following the practice of behavior-driven development (BDD) covering 95% of the code.
  • Architected and built pages of the front-end app in jQuery.
Technologies: Docker, Bootstrap, jQuery, MySQL, Express.js, Node.js, Microservices, REST, REST APIs, Code Architecture, Full-stack Development, Web Development, Full-stack, DOM, APIs

Software Developer

2013 - 2014
  • Modernized the JavaScript code of the front end by dividing it into libraries, increasing its simplicity and readability.
  • Created a reusable module using Java to generate PDF documents based on data from a database and HTML forms and integrated it with an existing product.
  • Built new pieces of the application from top to bottom using Java, JavaScript, HTML, CSS, and SQL.
  • Fixed bugs and adjusted the product's back and front end for clients' needs.
Technologies: Java, JavaScript

Web Developer

2007 - 2014
Independent Work
  • Built full websites using Python, Django, HTML, CSS, and JavaScript.
  • Designed a relational database for the use of websites.
  • Developed software using RESTful APIs with Node.js and Express.js.
  • Designed and implemented fully functional websites from top to bottom.
  • Worked with clients on planning and designing products.
Technologies: SQL, CSS, HTML, Django, Python, Web Development


I developed an internet platform for finding people with similar interests and problems to collaborate.

Ditup provides a place where people with similar interests, problems, or needs can meet and connect.

• Refactorized part of the validating process on the Node.js/Express.js query path by implementing a parser used as one of the pieces of middleware software.
• Designed and implemented REST API responses for various queries using Node.js and ArangoDB Query Language.
• Created and wrote tests for every implemented functionality following BDD standards.
• Used the JSON schema and JSON Web Token libraries to increase the website's security.

This open-source web app visualizes how well-known people influence each other based on linked data from

I developed this in collaboration with Michal Salajka.

The app runs in the following link:

Technologies: React, Redux, D3.js, SPARQL

Lisbon Nomadbase
A project exploring the ways to connect people who want to cooperate with each other.

Work Done:
• Co-founded and co-created the place.
• Managed and organized the space.
• Designed, developed, and maintained the website using Python Django.

Dictionary and Book Translator

An application which helps to read books in foreign languages by quickly translating words and creating dictionaries for a particular book.

It's focused on a simple and quick performance.
I researched, designed and implemented the whole project including, searching algorithm and graph database storage of data.

Technologies: Python, ArangoDB

Steganography-based Communicator Based on Different Types of Encryption

Based on steganography methods and cryptography algorithms, this communicator sends hard-to-detect-by-third-party messages and images through an HTTP protocol.

Technologies: C++, Java

Brontosaurus, A Platform for Managing Events and Users
Brontosaurus is an event organization platform that focuses on preserving nature and ecology by organizing events for children, teenagers, families, and adults.

The platform is designed to be intuitive and user-friendly for both event attendees and organizers. Users can easily browse events, view event details, and sign up for events of interest.

Organizers can create events, manage participants and applications, as well as create volunteering opportunities for members of

Working in a team of two, I was responsible for the entire process of designing, building, testing, and deploying the app. My main tasks included designing and implementing various components for managing app functionalities. I also added CSS styles to the whole app to make it visually appealing, easy to navigate, and accessible for users.

Given the importance of security, I worked closely with the back-end team to ensure the app was safe and connected the front-end with the API in Python Django. Throughout the project, I also tested the app and ensured all features worked correctly.

2009 - 2014

Bachelor’s Degree in Computer Science

Warsaw University of Technology - Warsaw, Poland


Node.js, React, REST APIs, jQuery, React Redux


Adobe Photoshop, Git, Sublime Text, GitHub, Figma


Express.js, JSON Web Tokens (JWT), Bootstrap, Redux, Hapi.js, Angular, AngularJS, Django, Cypress


JavaScript, SQL, CSS, HTML, Python, SCSS, GraphQL, HTML5, C, Java, Less, TypeScript, C++, ECMAScript (ES6)


ArangoDB, JSON/XML Schemas, NoSQL, Relational Databases, MySQL, PostgreSQL


REST, Pair Programming, Object-oriented Programming (OOP), Test-driven Development (TDD), Behavior-driven Development (BDD), Design Patterns, Testing, Unit Testing, Microservices, Automation


MacOS, Firebase, Linux, Docker, Windows, Amazon Web Services (AWS), Visual Studio Code (VS Code)


Data Structures, Algorithms, Front-end, Web Development, Pixel Perfect, Responsive Web Apps, Storybook, Code Architecture, Full-stack Development, Full-stack, Artificial Intelligence (AI), Robotics, Accessibility, Design, Web Accessibility, DOM, APIs

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