Software Developer
I build reliable mobile, web, desktop, and API solutions with a focus on practical architecture and polished user experiences.
Background
About Me
A practical developer working across product interfaces, APIs, data, and connected systems.
Education
Graduate in Applied Computer Science from the University of Silesia in Katowice.
First Role (Maluka)
- .NET Desktop Developer
- Built an ERP-like system for inventory, orders, projects, invoices, and vendors.
Current Role (Ejsak Group)
- .NET & React Native Developer
- Developed mobile apps for sales, scheduling, API integration, and data handling.
- Developed Exhibition Management System.
Personal Projects
- Game bots
- Google review automation
- Vacation deal notifier
Interests
- Traveling
- Cycling
- Calisthenics
- Swimming
- Spending time with friends
Selected work
Projects
Commercial systems and personal products built across mobile, web, desktop, and API platforms.
Commercial project
EMS - Exhibition Management System
A web and server-based system for managing museum exhibitions and connected multimedia devices.
- Modular architecture built with Symfony (PHP) and React
- Device management integrated with a C#/.NET server application for real-time communication
- RESTful API endpoints for CRUD operations across all core modules
Key Features
- Modular architecture built with Symfony (PHP) and React
- Device management integrated with a C#/.NET server application for real-time communication
- RESTful API endpoints for CRUD operations across all core modules
- Media and Playlist modules for uploading, organizing, and assigning media to exhibition devices
- Advanced scheduling system for procedures and exceptions, allowing precise task execution at defined times and days of the week
- PostgreSQL database with entity-based validation and migration system
My Contributions
- Developed and extended server-side plugins in C#/.NET for device control and integration
- Designed and implemented new Media and Playlist modules in Symfony, including upload, pagination, and deletion endpoints
- Created database entities and migrations using Doctrine ORM
- Integrated EMS backend with external APIs
- Participated in designing and deploying new features across production environments
- Collaborated with frontend developers to align API response structures with React hooks (React Query, Axios)
- Installed and tested the entire system on various devices within production environments
C#.NETPHPSymfonyReactPostgreSQLTypeScriptAxiosAPIDoctrine ORMGitGitHubPostmanJira
Commercial project
Field Sales & CRM Mobile Apps
Mobile applications for field sales ambasadors, coordinators, and administrators, designed to streamline sales and customer management.
- CRM module for managing customer interactions and sales tracking
- Work hours tracking, visit scheduling, and task management
- Performance analytics and reporting for field sales representatives
Key Features
- CRM module for managing customer interactions and sales tracking
- Work hours tracking, visit scheduling, and task management
- Performance analytics and reporting for field sales representatives
- Real-time data synchronization with the backend API
- Local database integration with TypeORM and SQLite for efficient data storage
My Contributions
- Developed and maintained custom npm packages in TypeScript for API communication, data handling, and much more
- Implemented models, containers, extensions, database management logic, and various utilities for seamless API interaction
- Optimized database interactions and query performance using TypeORM and SQL
- Collaborated on the backend by analyzing and enhancing PHP API logic to ensure stability and proper integration
- Assisted in frontend development and troubleshooting issues across the system
TypeScriptReact NativeExpoC#PHP.NETAPISQLiteTypeORMnpmAxiosSQLGitGitHubMicrosoft SQL ServerJiraPostmanJest
Commercial project
Biodiversity Educational Games Platform & CMS
A web-based platform for managing biodiversity learning content, operator-controlled gameplay sessions, and live scoring across multiple interactive educational games.
- Modular backend API for player registration, content delivery, gameplay sessions, scoring, and CMS operations
- Dedicated CMS for managing educational content across six thematic areas and basic or advanced difficulty levels
- Structured editors for eight content-driven game mechanics, including questions, answers, scoring rules, timelines, puzzles, and media-backed options
Key Features
- Modular backend API for player registration, content delivery, gameplay sessions, scoring, and CMS operations
- Dedicated CMS for managing educational content across six thematic areas and basic or advanced difficulty levels
- Structured editors for eight content-driven game mechanics, including questions, answers, scoring rules, timelines, puzzles, and media-backed options
- Validated, version-numbered JSON content packs with JSON and ZIP import and export workflows
- Image, audio, and video asset upload, preview, validation, cleanup, and delivery
- Operator-controlled session lifecycle with game selection, pause and resume controls, and player monitoring
- Transactional scoring and a separate live ranking view updated through WebSocket events with polling fallback
My Contributions
- Developed the complete Node.js and Fastify backend, organizing REST and WebSocket endpoints for authentication, content, sessions, players, scoring, and rankings
- Designed PostgreSQL schemas and migrations for sessions, players, and score events, including transactional score updates and leaderboard queries
- Built the React and TypeScript CMS frontend with dedicated editors for eight content-driven game mechanics and per-area, per-level configuration
- Created shared TypeScript contracts and Zod schemas for content packs, scoring configuration, game-specific fields, and asset references
- Implemented JWT-based CMS, operator, and player access flows with protected session and content-management operations
- Integrated media upload and deletion, JSON and ZIP import and export, content version increments, and missing-asset safeguards
- Participated in designing and implementing communication between the CMS, API, filesystem-backed content packs, PostgreSQL runtime data, and live ranking updates
TypeScriptReactNode.jsFastifyPostgreSQLREST APIWebSocketZodJSON Web TokensVitepnpmDockerNginx
Commercial project
Warehouse Management App
A desktop application for managing warehouse operations, orders, products, projects, invoices, and vendors
- Full CRUD operations integrated with an SQL database for robust data handling
- Project import and visualization in an expandable tree structure
- Inventory tracking with real-time status of reserved, ordered and available components
Key Features
- Full CRUD operations integrated with an SQL database for robust data handling
- Project import and visualization in an expandable tree structure
- Inventory tracking with real-time status of reserved, ordered and available components
- Optimized workflows for order processing and resource management
- User-friendly interface enhancing warehouse and supply chain efficiency
.NETC#Windows FormsSQLNuGetGitGitHub
Personal project
GitHubCarMinder Mobile App
A mobile app for managing vehicles and tracking maintenance, built with React Native
- Secure login and registration with email confirmation
- Manage vehicles by adding, editing, and deleting with data auto-fill from CarQuery API
- Upload and update vehicle photos
Key Features
- Secure login and registration with email confirmation
- Manage vehicles by adding, editing, and deleting with data auto-fill from CarQuery API
- Upload and update vehicle photos
- Parking spot tracking with GPS integration
- Maintenance reminders and notifications
- Offline data caching with server synchronization for seamless data management
- Intuitive UI with smooth navigation
TypeScriptReact NativeAxiosAsyncStoragenpmAPIGitGitHub
Personal project
GitHubCarMinder API
An ASP.NET Core API enabling secure data management for the CarMinder mobile app
- Secure authentication system with JWT tokens and Microsoft Identity
- User account management including registration, login, email confirmation, and logout
- Managing vehicle data (add, edit, remove, and retrieve user vehicles)
Key Features
- Secure authentication system with JWT tokens and Microsoft Identity
- User account management including registration, login, email confirmation, and logout
- Managing vehicle data (add, edit, remove, and retrieve user vehicles)
- Secure communication between mobile app and backend with API endpoints
- Integration with Entity Framework Core for efficient database operations
- Email notifications using MailKit
- Comprehensive API documentation via Swagger (Swashbuckle)
.NETC#Entity Framework CoreNuGetMicrosoft SQL ServerSwaggerMailkitGitAPIPostmanGitHub
Personal project
GitHubFinance Tracker
A web application built with ASP.NET Core for managing personal finances
- Transaction categories management (add, edit, delete categories for better organization)
- Transactions management (add, edit, and delete financial transactions)
- Dashboard overview with real-time financial insights
Key Features
- Transaction categories management (add, edit, delete categories for better organization)
- Transactions management (add, edit, and delete financial transactions)
- Dashboard overview with real-time financial insights
- Visual charts for expense distribution and income vs expense comparison
- Recent transactions table for quick access to financial activities
- Integrated currency converter with real-time exchange rates from the Currency Rates API
- Import and export functionality for easy data management and backup
.NETC#HTML5CSS3Entity Framework CoreNuGetMicrosoft SQL ServerSyncfusionData VisualizationCurrency APIGitPostmanGitHub
Toolbox
Skills & Technologies
Technologies used across production backend, mobile, desktop, data, and infrastructure projects.
Backend & APIs
Backend services, real-time communication, authentication, validation, and integrations.
- Node.js
- Fastify
- Symfony
- .NET / ASP.NET Core
- REST APIs
- WebSockets
- JWT
- Zod
Languages
Programming languages used across production systems and personal projects.
- TypeScript
- C#
- PHP
- Python
- Rust
- C++
- C
Databases & Persistence
Databases, schema design, migrations, transactions, and data access.
- PostgreSQL
- SQL Server
- SQLite
- Entity Framework Core
- TypeORM
- Doctrine ORM
- Database Migrations
- Transactions
Frontend & Mobile
Web interfaces, CMS applications, and cross-platform mobile development.
- React
- React Native
- Expo
- Vite
- HTML5
- CSS3
Infrastructure & Deployment
Containerized environments, Linux servers, reverse proxies, and production deployments.
- Docker
- Nginx
- Linux (Ubuntu, Debian)
- Azure
- VPS Management
- Bash
Tools & Testing
Version control, testing, API diagnostics, package management, and team workflows.
- Git
- GitHub
- Jest
- Postman
- Jira
- npm / pnpm
- Swagger / OpenAPI
Get in touch
Let’s Build Something Useful
Feel free to reach out by email or connect through one of my professional profiles.
© 2026 Miłosz Jonak. Built with Next.js.