Sasa Kostadinovic, Developer in Niš, Serbia
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Sasa Kostadinovic

Verified Expert  in Engineering

Full-stack Developer

Niš, Serbia
Toptal Member Since
November 18, 2019

Sasa is a versatile full-stack engineer and architect with over a decade of professional experience. He excels at developing scalable and complex solutions using various programming languages and platforms such as .NET, Angular, Scala, and Play. He is highly focused on code quality, testability, and simplicity, and he also tends toward functional programming and a practical way of thinking.


CodeRain Solutions
SQL, Functional Programming, Rx, Docker, Bootstrap, JavaScript, TypeScript...
.NET, C#, .NET Core, Angular, TypeScript, JavaScript, SCSS, HTML, HTML5, REST...
Microservices Architecture, SQL, Windows Presentation Foundation (WPF)...




Preferred Environment

Git, JetBrains, Visual Studio, Windows, MacOS, Best Practices, Object-oriented Programming (OOP), Software Design Patterns

The most amazing...

...thing I've developed is a GDPR-compliant software solution that helps corporations in their GDPR regulation strategy.

Work Experience

Solution Architect | Software Engineer | Founder

2018 - PRESENT
CodeRain Solutions
  • Created various web and API-based business solutions using cutting-edge technologies. Covered different industries such as robotics and automation, agriculture, outsourcing, and many more.
  • Used C#, .Net Core, Scala, Play, Angular, TypeScript, JavaScript, HTML, CSS, RxJS, JWT, Bootstrap 4+, Flask, and many other technologies on a regular basis.
  • Built a strong bond of trust with all clients. Loyalty and transparency are always high priorities.
  • Worked effectively on the deployment and process automation using shell scripts and Docker.
  • Contributed continuously to security and privacy improvements such as secure data transfer, preventing sensitive data exposure, password hashing, OAuth, preventing XSS and CSRF/XSRF attacks, and others.
  • Participated in small and large teams following all Agile principles.
Technologies: SQL, Functional Programming, Rx, Docker, Bootstrap, JavaScript, TypeScript, HTML, Python, Angular, Play, Scala, C#, Full-stack, ASP.NET, ASP.NET MVC, C#.NET, Best Practices, Object-oriented Programming (OOP), Software Design Patterns, CSS

Senior Full-stack Engineer

2020 - 2021
  • Contributed to the full-stack development in all areas of the web application, such as the back end in C# and the front end in Angular.
  • Participated in technical discussions and decisions.
  • Worked with stored procedures and query optimization on MSSQL database with tables containing millions of rows.
  • Involved in production releases, leading some of them.
  • Implemented Sign in with Apple features and took part in its implementation with Google.
  • Delivered pixel-perfect and responsive designs. Mastered CSS styling along the way by using Material Design and SCSS.
  • Took an important part in various report implementations, such as HTML, PDF, and CSV, using different technologies such as Chart.js, iTextSharp, and Browserless.
  • Involved in Azure DevOps tasks related to CI/CD pipelines and various configurations.
Technologies: .NET, C#, .NET Core, Angular, TypeScript, JavaScript, SCSS, HTML, HTML5, REST, REST APIs, Material Design, Angular Material, Pixel Perfect, CSV, Reports, Reporting, Microsoft SQL Server, SQL Stored Procedures, Stored Procedure, JSON Web Tokens (JWT), GitHub, Slack, Azure DevOps, Single Sign-on (SSO), Chart.js, ASP.NET, ASP.NET MVC, C#.NET, SQL, CSS

Software Engineer | Network Administrator

2013 - 2018
  • Contributed to the improvement and feature implementation of various desktop products from the Ikena family. The products were mainly associated with advanced image processing, real-time video enhancement, computer vision, and GIS.
  • Built the external REST API and microservices ecosystem used for image enhancements and video/audio redaction.
  • Helped with the integration of image recognition, object detection, and tracking features into specific products. Collaborated with machine learning and the core C++ team.
  • Participated in the implementation of a GIS module. Created the UI and middleware logic of the module. The module was used to map real-time video location points to a 3D globe.
  • Administrated the computer network. Upgraded company devices with the latest security patches. Protected and secured external network access. Physically secured equipment and ports.
  • Used C#, Python, Flask, SQL, Docker, and many other technologies on a regular basis.
Technologies: Microservices Architecture, SQL, Windows Presentation Foundation (WPF), Windows Forms (WinForms), Docker, TypeScript, JavaScript, CSS, HTML, JSON Web Tokens (JWT), Flask, Python, C#, ASP.NET, ASP.NET MVC, C#.NET, Best Practices, Object-oriented Programming (OOP), Software Design Patterns

Software Engineer

2011 - 2013
IRVAS International Ltd.
  • Applied different solutions related to the consumption of electric energy, reporting tools, and enterprise resource planning (ERP) systems.
  • Created a fast software reporting tool using HDF5 storage format and Python libraries. The output of the reporting tool was a detailed chart report as a result of processing a large, time-based data set.
  • Built a desktop application used for communicating with a smart electric meter that supports reading and writing operations. Used the DLMS/COSEM protocol.
  • Implemented various Odoo (former OpenERP) modules covering accounting, eCommerce, inventory, and process automation.
  • Worked on the implementation of a web application that controls, monitors, and collects readings from smart meter devices. In addition to standard readings like power consumption, the app was supposed to detect anomalies and properly alert users.
  • Used C#, CSS, JavaScript, HTML, and many other technologies on a regular basis.
Technologies: NumPy, Matplotlib, JavaScript, CSS, HTML, Windows Forms (WinForms), Odoo, Python, C#, ASP.NET, ASP.NET MVC, C#.NET, SQL

Educational Fitness Platform (via Toptal)

Online fitness software allows teachers and coaches to deliver physical education and athletic development programs built by industry professionals. Students get detailed, step-by-step instruction right on their mobile devices and web platforms, while teachers and coaches can track engagement and progress through any metrics they choose.

The solution consists of various components and supports hundreds of thousands of users. As a full-stack engineer, I primarily worked on all parts of the web application. This involved work on the front end using Angular and the back end using .NET and .NET Core technologies with an extensive SQL database. In addition to the many features implemented, some of the most important include the implementation of single sign-on, support for different types of reports, and pixel-perfect design.

Technologies: .NET, .NET Core, C#, Angular, JavaScript, TypeScript, Microsoft SQL Server, Material Design, Chart.js, CSS, HTML, JSON Web Tokens (JWT), GitHub, CSV and PDF export, iTextSharp, browserless, Azure DevOps, and single sign-On (SSO).

GDPR Management Tool

An online enterprise solution used for handling GDPR.

The software answers the EU General Data Protection Regulation and takes care of all aspects of data protection and privacy inside a large company. It helps a corporation handle data subject requests and quickly respond in multiple languages.

FertiCalc Software

A web-based software solution used to get the best results from cultivated crops.

The software is supposed to calculate the necessary formulations and the amount of fertilizer to give farmers the ultimate yield of cultivated crops. In addition, the solution should improve the daily routines and tasks of the company's agronomists.

Technologies used: Angular, Python, Flask, PostgreSQL, Docker, Bootstrap, TypeScript, CSS, JavaScript, and REST API.

Motion Control Manager

A software solution used for executing commands triggered by a motion control device using hand gestures. As a result, each command interacts with the existing user interface in some way.

The idea was to improve the efficiency of the day-to-day tasks of a large company with a motion control device and hand gestures in front of the big screen.

Technologies used: C#, .NET, Nginx, JavaScript, JQuery, CSS, HTML, Bootstrap, and REST API.

Sales Results Portal

A web portal used by sales managers in order to track their results. The application visualizes current achievements and goals. It provides tons of features such as exporting results, emailing, handling campaigns, etc.

Technologies used : .NET, C#, MS SQL, JQuery, Bootstrap, JavaScript, CSS, HTML.

Sports Betting Web Platform

I worked on various tasks for a lean startup company with a unique product designed to build tools and provide education and resources to the sports betting community.
In a nutshell, the project aggregates sports data. Data is used later via platform-integrated tools, which allows sports betting enthusiasts to find value in the market. This is all based on proprietary data science models.
2006 - 2012

Master's Degree in Software Engineering

Faculty of Electronic Engineering - Niš, Serbia


Programming with Google Go Specialization



scala-reactiveX: Programming Reactive Systems



Cisco CCNA

Cisco Network Academy - Niš


Windows Forms (WinForms), Reactive Extensions, jQuery, Slick, RxJS, REST APIs, LINQ, React, Scala.js, Matplotlib, NumPy, D3.js, SQLAlchemy, Chart.js, Leaflet


JetBrains, Visual Studio, Git, Odoo, GitHub, Slack


ASP.NET Core, Angular, .NET Core, .NET, ASP.NET, ASP.NET MVC, Bootstrap, Angular Material, Rx, Flask, Play, JSON Web Tokens (JWT), Razor, Redux, Next.js, Lagom, Akka, Windows Presentation Foundation (WPF), Play Framework


C#, TypeScript, HTML5, C#.NET, Scala, Python, HTML, CSS, JavaScript, SQL, CSS4, Sass, Go, SCSS, Stored Procedure


Best Practices, Object-oriented Programming (OOP), Scrum, Agile, Functional Programming, Test-driven Development (TDD), Automation, DevOps, Reactive Programming, Microservices Architecture, Azure DevOps, REST


Software Design Patterns, Amazon Web Services (AWS), Docker, MacOS, Linux, Windows, AWS Lambda, Amazon EC2, Microsoft, Apache Kafka, Azure


Relational Databases, SQL Stored Procedures, PostgreSQL, Microsoft SQL Server, JSON, MySQL, Amazon S3 (AWS S3), Cassandra, Databases

Industry Expertise



Full-stack, APIs, Back-end, Front-end, Front-end Development, Material Design, Web Scraping, Lambda Functions, Solution Architecture, Cloud Security, Serverless, Architecture, Robotics, App UI, Charts, Data Visualization, CSV, PDF, Single Sign-on (SSO), Reports, Reporting, Pixel Perfect, Microsoft Azure, AWS Management Console, High-load

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