Mihael Pejak, Developer in Zagreb, Croatia
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Mihael Pejak

Verified Expert  in Engineering

Software Developer

Zagreb, Croatia
Toptal Member Since
December 30, 2016

Mihael has been a developer for 10+ years—with 7+ years of experience working with the .NET framework, large system integrations, and enterprise solutions for various industries. He also has a master's degree in information systems. He specializes in enterprise-level application development on the .NET platform. Mihael has worked on numerous successfully delivered projects—working on the front-end and back-end.


TSystems International (via Toptal)
Continuous Integration (CI), Code Review, Azure DevOps, Git, Code Architecture...
Company in Telecommunications Industry (via Toptal)
C#.NET, Amazon CloudFront CDN, Amazon S3 (AWS S3)...
JavaScript, HTML, RabbitMQ, Microsoft SQL Server...




Preferred Environment

SQL Server Management Studio (SSMS), TFS, Visual Studio

The most amazing...

...thing I've coded is a Radius server (VASCO) TCP client library that enables two-factor authentication for user management solutions.

Work Experience

Software Engineer / Expert on Authorization and Authentication in Azure

2020 - 2020
TSystems International (via Toptal)
  • Designed the architecture and developed a modular SSO authentication and authorization system capable of handling complex access rights using groups, roles, and users.
  • Implemented the REST API's using .NET Core 3.0 to expose the authorization system to the front-end applications and other parts of the system.
  • Designed the database model for the authorization system. Implemented the database schema, authorization and reporting procedures, and functions in Microsoft SQL Server 2019.
  • Designed UX wireframes for user management and oversaw front-end development based on Angular 9.
  • Gathered, analyzed, and documented requirements from the customer. Designed architecture diagrams and kept up to date documentation using Azure DevOps Wiki.
  • Followed Scrum methodology for software development and collaborated with an Agile product team using the latest best practices including code reviews and continuous integration via Azure DevOps.
Technologies: Continuous Integration (CI), Code Review, Azure DevOps, Git, Code Architecture, Agile, JSON Web Tokens (JWT), REST APIs, REST, Single Sign-on (SSO), Authentication, Authorization, Angular, Azure, C#.NET, C#, Microsoft SQL Server, Entity Framework Core, ASP.NET Core, .NET Core

Full-stack Developer

2017 - 2020
Company in Telecommunications Industry (via Toptal)
  • Designed and implemented an OTT cloud video platform. The platform enabled users to have a video on demand, live streaming, and document sharing to provide interactive training content for company employees at 700 worldwide locations.
  • Developed front-end portals for client applications for video on demand, live streaming, document sharing, and administration with real-time analytics using TypeScript and Angular.
  • Developed REST API's using C# and ASP.NET to expose the platform to the front-end applications, as well as WCF services to connect the system itself between various modules.
  • Designed and implemented database schema, procedures, and functions for the platform using MS SQL Server. Implemented detailed reporting which provided stakeholders with information about employee training status.
  • Developed a studio Windows Forms application that enabled a director to share a live stream from a camera or a presentation, communicate with the audience via Webphone, and bring up poll questions connected to the analytics.
  • Integrated the platform with AWS Cloudfront and on-premise media appliances written in Node.js to enable streaming services to users based on their location.
  • Implemented a service using MongoDB and ASP.NET to enable real-time messaging between users in a live session.
  • Worked on an interactive map portal that displayed information about media appliance failures written in .NET Core and React.
  • Set up continuous integration for the platform using Azure DevOps.
  • Contributed my software engineering expertise from gathering requirements, writing technical documentation and architecture diagrams, to production deployment and product maintenance.
Technologies: C#.NET, Amazon CloudFront CDN, Amazon S3 (AWS S3), Windows Communication Framework (WCF), REST APIs, Code Architecture, Azure DevOps, Node.js, WebPhone, Windows Forms (WinForms), .NET Core, MongoDB, React, Angular, TypeScript, JavaScript, Microsoft SQL Server, ASP.NET, .NET, C#

Software Engineer Specialist

2013 - 2017
  • Researched and implemented new technologies into existing and new solutions.
  • Created sophisticated and efficient back-end components for a large scale on-demand provisioning system.
  • Designed and implemented reusable components that were used through many solutions in the company.
  • Deployed the solutions through various test, integration, and productions environments.
  • Served as a technical resource and a mentor for junior engineers.
Technologies: JavaScript, HTML, RabbitMQ, Microsoft SQL Server, Windows Communication Framework (WCF), ASP.NET

Software Engineer

2010 - 2013
  • Gathered requirements from customers and wrote functional specifications.
  • Designed, developed, and implemented web services using the .NET Windows Communication Foundation framework.
  • Designed, developed, and implemented real-time web applications based on ASP.NET MVC and ASP.NET Web API.
  • Worked on large infrastructure provisioning systems handling thousands of requests per day.
  • Adhered to the best design patterns and practices while designing and developing solution components.
Technologies: JavaScript, HTML, ASP.NET Web API, Microsoft SQL Server, Windows Communication Framework (WCF), ASP.NET

Junior Software Engineer

2009 - 2010
  • Studied the requirements of the clients and specific needs of the projects.
  • Developed and implemented web applications based on ASP.NET MVC.
  • Designed, implemented, and customized databases using Microsoft SQL Server.
  • Wrote unit tests using MSTest framework to ensure product quality.
  • Adhered to the best standards and practices for developing .NET applications.
  • Documented the design and code specifications accurately.
Technologies: MSTest, JavaScript, HTML, Microsoft SQL Server, ASP.NET

User Management Solution

I worked in a team developing a single-sign on application for a company in Europe. The application was integrated with Active Directory and supported third-party authentication for the company's SaaS applications. I wrote a TCP client for the integration with the VASCO service to enable two factor authentication. The application is currently in production with 20,000 users.

Network Provisioning Engine

I worked on the development of a portal for network infrastructure management. The service enables users to manage network, firewall and load balancing rules on their infrastructure. The solution is composed of the front-end portal, the queue engine, the back-end component and the infrastructure provider. I developed the portal using the ASP.NET MVC framework, and connected it to the back-end components using WCF services.

Point of Sale Solution

I worked on the development of a cash register application for medium-sized retail customers. I developed the component responsible for the integration with the tax administration. The solution had to be optimized to finish the invoicing operation in a few seconds—from sending the invoice to the tax administration via SOAP to printing the invoice on a portable printer. The component was reused by various companies entering the Croatian market.


C#, T-SQL (Transact-SQL), JavaScript, HTML, TypeScript, C#.NET, Visual Basic .NET (VB.NET), CSS, Java


.NET, ASP.NET Core, .NET Core, ASP.NET MVC, ASP.NET, ASP.NET Web API, Windows Communication Framework (WCF), AngularJS, Angular, Entity Framework Core, JSON Web Tokens (JWT)


Entity Framework, Windows Forms (WinForms), React, REST APIs, Node.js, SignalR, jQuery


Visual Studio, SQL Management Studio, TFS, MSTest, RabbitMQ, WebPhone, Amazon CloudFront CDN, Git


Object-oriented Programming (OOP), Design Patterns, Agile, REST, Dependency Injection, Asynchronous Programming, Service-oriented Architecture (SOA), Azure DevOps, Continuous Integration (CI), Waterfall Development


Amazon EC2, Azure, Windows, Amazon Web Services (AWS), Linux, Android


Microsoft SQL Server, Relational Databases, SQL Server Management Studio (SSMS), MongoDB, Amazon S3 (AWS S3), NoSQL


Ajax, SOAP, Authorization, Authentication, Single Sign-on (SSO), Code Architecture, Code Review

2009 - 2014

Master's Degree in Information Systems

University of Applied Sciences Velika Gorica - Velika Gorica, Croatia

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