Svetlozar Valchev, Developer in Sofia, Bulgaria
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Svetlozar Valchev

Verified Expert  in Engineering

Full-stack Web Developer

Sofia, Bulgaria
Toptal Member Since
December 10, 2018

Svetlozar is a senior-level full-stack programmer with a demonstrated history of working in various industries, including gaming, eCommerce, insurance, finance, telecommunications, healthcare, and many others. His experience with full-lifecycle work across multiple fields makes him a valuable asset to any team. Svetlozar is very flexible and has a proven ability to adapt. He is also a fast learner with a passion for technology and innovation.


Triforce Studio Ltd.
JavaScript, React Native, Node.js, PostgreSQL, Vue, Prisma, Three.js, Unity...
Hihve LLC
HTML, JavaScript, CSS, WebGL, React, Next.js, AWS Lambda, Node.js, PostgreSQL...
Toptal Contractor Work
PHP, Laravel, React Native, React, CSS3, HTML, JavaScript




Preferred Environment

Git, WebStorm, Ubuntu, Windows, Visual Studio Code (VS Code)

The most amazing...

...aspect of programming is the drive for constant improvement, learning, and pushing yourself to achieve things you didn't know you could do.

Work Experience

Co-founder, Software Engineer

2022 - PRESENT
Triforce Studio Ltd.
  • Developed a mobile app for both iOS and Android using React Native Expo.
  • Built a back office tool to allow full control of the game parameters.
  • Designed and optimized a database server to support many concurrent users.
  • Developed a REST API back end to supply the back office and mobile app with data.
  • Handled CI/CD with zero-downtime deployment using Digital Ocean services.
Technologies: JavaScript, React Native, Node.js, PostgreSQL, Vue, Prisma, Three.js, Unity, WebGL, PixiJS, React, Express.js, CSS3, HTML, TypeScript

Front-end Developer

2023 - 2024
Hihve LLC
  • Engineered a social media sports app empowering athletes to create and share digital cards on their profiles.
  • Researched and constructed a scalable back-end infrastructure to efficiently convert canvas to video, improving platform performance and usability.
  • Pioneered the development of a template builder utilized internally by team members to effortlessly craft digital cards, enhancing productivity and creativity.
  • Collaborated closely with artists to establish a streamlined workflow for generating new assets, ensuring scalability and consistency across the platform.
Technologies: HTML, JavaScript, CSS, WebGL, React, Next.js, AWS Lambda, Node.js, PostgreSQL, Adobe Animate, FFmpeg, CreateJS, Vercel

Full-stack Developer

2023 - 2023
Toptal Contractor Work
  • Developed and maintained a back end and a database that are used to supply data to the mobile client.
  • Developed a mobile app for both iOS and Android using React Native.
  • Assisted with managing scope, schedule, and deadlines.
Technologies: PHP, Laravel, React Native, React, CSS3, HTML, JavaScript

Founder, Game Developer

2021 - 2023
Software Dev Ltd.
  • Developed gameplay logic for the game such as character movement, gameplay mechanics, etc.
  • Designed and developed networking code to support up to 24 players per session.
  • Worked on and executed game designing, balancing, and gathering feedback.
  • Assisted in kitbashing, creating environment art, and level designing.
  • Managed a team of developers, artists, and community managers.
Technologies: Lua, Unity, CSS3, HTML

Senior Full-stack Developer

2019 - 2020
Toptal Contractor Work
  • Developed and maintained a complex nursing and patient management software for use by multiple hospitals.
  • Built a platform for tracking various statistics of patient accommodation.
  • Created a platform for bed and ward management to track where patients should go.
  • Developed various back-end tools to integrate API from physical machines to upload data to the server.
  • Designed and developed a dashboard for tracking patients in an elderly care home.
  • Built other systems, libraries, and components to help visualize the healthcare service quality and improve the overall experience and ease of use.
Technologies: JavaScript, Aurelia, Vue, Node.js, HL7 FHIR Standard, SMART on FHIR, Fast Healthcare Interoperability Resources (FHIR), WebGL, Nuxt.js, Angular, Three.js, Express.js, CSS3, HTML, TypeScript

Software Engineer

2016 - 2019
Minerva Networks
  • Developed and maintained a custom JavaScript framework.
  • Developed an app that runs on hardware with minimal computing power.
  • Frequently refactored and rewrote to improve performance.
  • Researched and developed new frameworks and approaches to improve development flow with customer requirements while maintaining good performance.
  • Improved user experience with faster load times, animations, and improved input response time.
  • Introduced data modeling and cache mechanisms to reduce the number of calls to the back end, greatly increasing the maximum number of concurrent users to several million.
Technologies: TypeScript, Node.js, Webpack, Grunt, EJS, Knockout (Knockout.js), RequireJS, Perforce, JavaScript, CSS, HTML, CSS3

Full-stack Developer

2014 - 2016
DSP Media Group
  • Prototyped and developed a mobile app using Angular and Cordova.
  • Developed the back office front-end using Aurelia and
  • Built the back end infrastructure using a technology stack that includes Express.js, Redis, and MongoDB.
  • Developed middleware and API gateways that handled external APIs.
  • Assisted in managing project tasks and scope using Jira.
  • Automated and improved the development flow using Slack and Bots.
Technologies: Amazon Web Services (AWS), Slack, Jira, APIs, Express.js, Socket.IO, Aurelia, Cordova, Angular, Git, Redis, MongoDB, Node.js, JavaScript, CSS, HTML, CSS3

UI Engineer

2015 - 2015
  • Developed and maintained the game UI using Angular 1.5.
  • Attached game logic to UI using Lua exposed by the game code.
  • Assisted in brainstorming and designing the UI/UX.
Technologies: AngularJS, Subversion (SVN), Lua, JavaScript, CSS, HTML, CSS3

HTML5 Game Developer

2012 - 2014
Cayetano Gaming
  • Developed a custom JavaScript-based game engine to use in-house.
  • Developed slot and scratch games using the in-house game engine.
  • Scripted animations provided by animators (sprite sheets, custom animations using Tween.js, and other approaches).
  • Edited audio, including cutting and splitting using tools like Audacity.
  • Supported a wide range of mobile devices and tablets.
  • Developed build tools using Node.js for automatization and automatic deployments.
Technologies: Node.js, Grunt, CreateJS, Zepto, Subversion (SVN), JavaScript, CSS, HTML, PixiJS, CSS3

Web Developer

2011 - 2012
  • Integrated many payment providers (Paypal, Skrill, PaySafe, ePay, and others).
  • Created a recurring payments system integrated it with payment providers.
  • Developed and maintained business and sales analytics tools.
  • Improved back-office customer support management tools.
  • Supported a payments system using an MVC architecture.
  • Resolved payment and chargeback issues and tickets.
  • Developed an app in Python that automates the invoice export function.
Technologies: jQuery, Python, Subversion (SVN), MySQL, PHP, JavaScript, CSS, HTML, CSS3

Web Developer

2008 - 2009
  • Created a custom MVC framework to improve the development workflow.
  • Developed corporate websites using Joomla and other CMSs.
  • Developed blogs and websites using WordPress and other blogging frameworks.
  • Transformed PSD files from designers to HTML and CSS.
  • Developed an email template engine for sending emails to thousands of subscribers.
Technologies: jQuery, WordPress, MySQL, PHP, JavaScript, CSS, HTML, CSS3

STB Web Client

Web client that runs on a Set-Top Box. My role in this project is to develop and maintain the web client in a team of 8 people. The STBs are very limited in computing power, which requires a very light-weight in-house framework to ensure that the UI runs smoothly. We constantly research and experiment with new approaches and frameworks that fit the often changing client requirements while using the best industry practices.

Insurance Broker Back Office

Developed the back end and front end of an Insurance Broker Software in a team of 3 people using the latest technologies. We had to work closely with the clients to ensure that the expectations match the product requirements. The main goal of the product was to automate the B2C insurance purchases as well as offer the option for insurance brokers to manage and scale their business.

BeamNG.Drive UI
Led the UI/UX development of the game BeamNG.Drive in a team of three people. I selected the technologies, frameworks, and UI direction. Ease of use, accessibility, and performance were significant priorities.

Traffic Manager Mod for Cities: Skylines
Developed one of the largest mods for Cities: Skylines which allows you to micro-manage the AI traffic using traffic lights, priority signs and lane restrictions. It was released under MIT License and had about 100,000 subscribers at the time of support.

Latest supported version is called 'Traffic Manager: President Edition' and has almost 800,000 subscribers.

Mobile Slot Games Framework

Mobile Slot Games for Paddy Power's subsidiary Cayetano Gaming. My role in this project was to develop and maintain a game engine (framework) in a team of 6 people, with reusability and modularity as our main focus. Created games using the framework by plugging the desired features and developing new ones if needed.

Payment System

Payment System for XS-Software's games. It's used to buy in-game currency using several payment providers. My role in this project was to implement new features like recurring payments and promotional offers, integrate new payment providers, and improve the user experience.

Glory Knights

A web-based game from the golden age of web-based games. I was the creator and lead developer. I managed a team of four people: two community managers, a designer, and a developer. It had some success and managed to gather about 50,000 registered users with 250-500 active average users.
2003 - 2011

High School Diploma in English, Mathematics, Informatics

Professional High School of Science and Mathematics 'Ivan Vazov' - Dobrich, Bulgaria


Node.js, jQuery, Socket.IO, RequireJS, React, Vue, Three.js, WebGL, Zepto, CreateJS, EJS, FFmpeg


NPM, Subversion (SVN), Bower, Gulp, Grunt, Webpack, Browserify, Git, GitHub, Prisma, Jira, Slack, Audacity, Perforce, Karma, Mocha, SMART on FHIR, Adobe Animate


Aurelia, Knockout (Knockout.js), Bootstrap, Express.js, React Native, Unity, Angular, Nuxt.js, PixiJS, AngularJS, Jasmine, Unity3D, Laravel, Next.js


TypeScript, HTML, CSS3, JavaScript, PHP, C#, Python, Lua, CSS


MVC Design, REST, Event-driven Architecture, Object-oriented Programming (OOP), Agile, E2E Testing, Unit Testing, Scrum, Agile Software Development, HL7 FHIR Standard, Fast Healthcare Interoperability Resources (FHIR)


MongoDB, MySQL, Redis, PostgreSQL


Windows, Ubuntu, Amazon Web Services (AWS), WordPress, Visual Studio Code (VS Code), AWS Lambda, Vercel


API Integration, Unidirectional Data Flow, Microsoft 365, State Machines, Games, Cordova, APIs

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