Sergi Wojtowicz, Software Developer in Warsaw, Poland
Sergi Wojtowicz

Software Developer in Warsaw, Poland

Member since June 17, 2019
Sergi is a software developer with over 15 years of professional programming experience. Over the years, he’s worked with a wide range of technologies creating web, mobile, and desktop applications, as well as gaining extensive experience with relational databases, including big data. Recently, Sergi has been fascinated by the next generation of programming languages—namely Kotlin and TypeScript—which he uses to create single-page applications.
Sergi is now available for hire




Warsaw, Poland



Preferred Environment

Ubuntu, Sublime, IntelliJ, GitLab

The most amazing...

...project I've participated in was a technology-independent environment that provides a unified web application interface.


  • IT Director | Co-founder

    2013 - PRESENT
    Genesis Mobo
    • Managed various projects (typically two to four in a year) in teams of 2-5 employees. Served as a senior developer on several projects using various technologies.
    • Designed a multi-modular architecture in which each module has a separate GIT code repository and can, therefore, be developed separately. The implementation was based on PHP (CodeIgniter), Javascript (AngularJS), Less (CSS) and npm was used to manage packages.
    • Managed the implementation of the application used to organize the traffic of over 1,000 city buses in real-time. He was responsible for creating the skeleton of a multi-module application based on CodeIgniter (PHP), jQuery (JavaScript) and PostgreSQL, as well as the implementation of selected modules.
    • Created many complex and optimal queries for the PostgreSQL database using the WITH clause to prepare data for the final query, as well as LAG and LEAD window functions.
    • Created an authorization engine for web applications based on Session Cookies and JWT in Ktor (Kotlin) together with an npm library written in Angular (TypeScript), which refreshes the token in the background every two minutes.
    • Created an application designed to report the number of passengers in vehicles presenting data both in tabular form, on charts and also on a map. The application has a report generator that allows the user to generate aggregate, statistical reports based on conditions defined by the customer. The application is based on Ktor (Kotlin), Angular (TypeScript) and the PostgreSQL database.
    Technologies: TypeScript, Kotlin, PostgreSQL, Java, PHP, JavaScript, Qt
  • Senior Developer | Project Manager | Co-founder

    2009 - 2017
    Mobo Studio
    • Implemented various games and applications for both iOS and Android.
    • Constructed a framework for iOS that provided a set of reusable components that was used to quickly implement presentation applications.
    • Developed a web application that allows the user to find vehicle or to check the occupancy of parking spaces based on the vehicle's GPS location.
    • Implemented parts of a platform built on Android which included among cryptography, an offline mode with data synchronization, registration, and blocking devices.
    Technologies: Java, Objective-C, PHP, JavaScript, PostgreSQL
  • Senior Java Developer | Project Manager

    2006 - 2009
    Cyberware Poland
    • Built a platform-independent framework that was used for CRM/ERP implementations and consists of auto-updates and support for CRUD based on XML form definition among other things.
    • Created a solution for digital newspapers. It consists of a Java desktop application where one could map areas of a PDF with content recognition to create ready-to-read articles and websites.
    • Extended or redefined with the help of Reflection, Java, AWT, and Swing components to implement a modern UX/UI (which was created by a designer on the project).
    Technologies: Java, PHP, PostgreSQL, JavaScript
  • Web Developer

    2004 - 2006
    Creaciones Virtuales
    • Implemented an MVC framework in PHP used by all of the company employees for development.
    • Created various websites and web applications for the public administration of Spanish provinces.
    • Invented, designed, and implemented a task-based system to replace assigning programming tasks in verbally or on paper.
    • Implemented a tool that was a Gantt financial chart used to plan the finances of provincial projects.
    • Established object-oriented programming in PHP, which has been appreciated and has become the company's standard.
    Technologies: PHP, JavaScript, MySQL, PostgreSQL, Flash, Java Applets
  • Web Developer

    2002 - 2004
    Freelance Work
    • Created a reusable CMS in PHP with authorization and content management.
    • Implemented support for the CMS into Flash for interactive websites.
    • Developed various websites for Polish companies and organizations based on a reusable CMS.
    Technologies: PHP, MySQL, Flash


  • Bus Traffic Management System (Development)

    I managed the implementation of the bus traffic management system while participating in it as a senior developer.

    The system is used every day during the organization of traffic of over a thousand buses using, among others, functions such as punctuality control, alarms in the event of irregularities, registration of communication events and vehicle failures. The system fully integrates with the solutions owned by the client, downloading the data it needs and providing data for other systems.

  • Customer Request System (Development)

    I built an application designed to handle customer requests for both software and hardware.

    The part intended for the customer is completely separated from the part used for handling notifications, also at the database level. The system integrates with the company's data sources. The functionality allows, inter alia, the flow of requests between IT and hardware departments, planning the sending of service technicians, and assessing the quality of service technicians' work.

  • Colorix Game (Development)

    I implemented Colorix, a game for Android and then also helped with implementation for iOS.

    Colorix is a match 3 puzzle game similar to Tetris. The game offers beautiful graphics that have been appreciated by critics. Both the Android and iOS versions were high in their category at one time. In addition, Apple chose the game as worth checking out and promoted it by placing it on the main page of its store for a week.


  • Languages

    PHP, JavaScript, TypeScript, SQL, Kotlin, Java, HTML, CSS
  • Frameworks

    CodeIgniter, Angular, AngularJS, Ktor, Angular Material, JSON Web Tokens (JWT)
  • Paradigms

    Object-oriented Programming (OOP), Imperative Programming
  • Storage

    PostgreSQL, JSON, PostGIS, MySQL
  • Other

    Web Applications, CSV, OpenStreetMap, FTP, Algorithms, Data Analysis
  • Libraries/APIs

    LeafletJS, Chart.js, jQuery
  • Tools

    Git, GitLab, Subversion (SVN), Redmine
  • Platforms

    Ubuntu, Software Design Patterns, MacOS


  • Bachelor's degree in Computer Engineering
    2000 - 2004
    University of Warsaw - Warsaw, Poland

To view more profiles

Join Toptal
Share it with others