Stefan Fischer, Developer in Bucheon-si, Gyeonggi-do, South Korea
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Stefan Fischer

Verified Expert  in Engineering

Software Developer

Bucheon-si, Gyeonggi-do, South Korea
Toptal Member Since
September 1, 2021

Stefan is an experienced C# and .NET developer and software architect, mainly focusing on back-end application services, yet having a broad range of professionally proven skills at hand to deliver end-to-end assistance on complex and challenging projects. He's also mastered various out-of-band skills in several fields of knowledge such as electronic design, 2D and 3D CAD construction, 3D printing, and manufacturing methods that help him quickly get to the idea of customer's specific needs.



Preferred Environment

Visual Studio 2019, .NET Core, Linux, Docker

The most amazing...

...project I've had is a real-time automated production data processing chain for industrial laser machines, turning raw requests into laid out production sheets.

Work Experience

Software Architect | Senior Full-stack Developer

2006 - PRESENT
  • Designed and implemented custom solutions of any scale for clients, either greenfield or integrated into complex landscapes using cutting-edge or legacy technologies as required.
  • Assisted customers with working out requirements and specifications and consulted on appropriate technologies for their problem field.
  • Collaborated with customer's in-house teams to hand over finished work results for production use, training, and continuous quality assurance.
  • Introduced and trained customers on new technologies if regarded beneficial for operation stability, budget-saving, or future-proofing.
  • Suggested improvements and proactively worked on customer's business processes, about how and where custom IT solutions could support overall operations.
Technologies: C#, .NET Core, Customer Service, Active Listening

Smart Screenshot Capturing Service

In a CNC machine shop, the shop owners usually don't have only the latest, cutting-edge technology machines but also legacy equipment that has to be monitored. Those legacy machines do not have dedicated maintenance interfaces available and had to be monitored by hand before.

The service we implemented with the clients automates this process by taking and analyzing screenshots and generating and reporting status information, thus enabling cloud monitoring for those legacy machines.

Just-in-time Job Generation for Industrial Lasers

Designed and implemented a microservice-based data processing chain to just-in-time create laid out and rendered production data for industrial laser machines.

Focused on high availability, fault tolerance, and easy integration at the far edge to ensure 24/7 operation of business-critical software. Implemented automated builds, deployments, and rolling updates on custom edge-deployed Kubernetes infrastructure.

Integrated the solution into customer's existing on-premise and far edge system environment for acquiring configuration data, layout data and reporting. Planned migration path for remaining legacy, custom-developed software.

Template Manager for Office

Designed and developed a set of add-ins for Microsoft Office (Word, Excel, and PowerPoint) to organize 100+ document templates within the customer's organization and make them available to employees.

The highlight feature was the ability to fill predefined, centrally managed customizable sets of employees' personal data into designated fields within the template.

VAT Filing for Freelancers

German freelancers and entities filing VAT reports have to file monthly VAT reports to be eligible for tax returns. This process is quite tedious and cumbersome if you have to go through your earning and expenses manually. Thus I architected and implemented an automated, desktop-based tool that retrieved this information from one's online bank account.

The client interfaced with online banking services via the standard HCBI protocol and submitted tax reports via government-provided XML REST services.

First only used for my own purposes, I also created a surrounding infrastructure to be used at a larger scale, including a web portal, automated client updates, and payment gateway.

R&D Embedded Systems | Back End and Cloud

Closely worked with my customer's on-site team in R&D on several consecutive, connected projects focused on IoT, embedded systems, and cloud-edge connectivity.

Developed front-end and back-end solutions for analyzing sensor data and IoT device control, using React, ASP.NET, REST APIs, and M2M protocols.

Being part of R&D allowed showcasing creative solutions in all involved stages and fields, using cutting-edge technologies for embedded, edge, back-end, and front-end systems.

Custom Retail Webshop

Being part of an on-site customer's team, I joined in developing a custom, from-scratch developed webshop system, personally accounting for the checkout system, including payment gateways.

Taking requirement inputs from specialist departments and working closely with the web design agency and integrating with the core framework were my main challenges.

SCCM 2012 Application Import Editor

Designed and implemented a domain-specific language (including a Visual Studio-based editor with auto-completion) to automate the task of importing new applications into SCCM 2012.

The project's primary goal was to provide application package owners (either employees or package scripters) with a tool to set up new deployments in a reliable and reproducible way.

The language is in a human-readable, text-based format; the editor also greatly improved productivity by allowing for collecting snippets of commonly repeating patterns and version control.

As icing on the cake, the editor's auto-completion feature was connected to the SCCM databases to retrieve and provide data on existing packages to speed up the authoring of new applications.

External Partner Integration API

Working with my customer's team, I designed and implemented REST APIs for external partner companies to automate tasks within the customer's web portal and database systems. Since being publicly visible and thus affecting customer's reputation and business revenue, a strong emphasis was laid on reliability and thorough quality control. Unit testing, automated rollouts, and consequent use of Agile methods were obligatory.

SCCM Self-service API

Designed and implemented a WCF service to integrate SCCM 2007 into a corporate employee self-service portal.

After introducing SCCM as the new software deployment platform, the customer's enterprise intranet employee portal integrated with self-service software ordering. The WCF service I developed served as the glue between both systems.

SCCM 2007 Export and Import Packager

Designed and implemented a desktop-based client to export and import full copies of SCCM entities (including all dependencies) to an archive file.

The customer used staging environments for his software deployment system to test new packages for quality and accuracy before the corporate-wide rollout. It was required that the production environment entities be an exact, deep copy of those in the testing stage systems. Thus we came up with an archive file-based export and import solution.

SCCM 2007 High-level API

Designed and implemented a customer-specific SCCM library, enabling the customer's developer team to interface their applications with SCCM 2007.

The goal of this project was to hide technical and implementation details of SCCM from the in-house developers who had no deeper experience with SCCM but had to integrate legacy corporate solutions with the newly introduced SCCM software deployment platform.

Server Installation Self-service Portal

Designed and developed an employee-facing web application to allow for customized, automated installation of test and production servers within the corporate network. The customer recently deployed SCCM 2007 as a new software deployment platform and wanted to neither grant excessive rights on the platform itself nor give extensive training on SCCM to the employees.

The project's goal was to provide a simplified, tailored-to-the-job front end that could be easily made available to all authorized employees without the need for training.

Software Release Cycle Management Portal

Supervised, maintained, and enhanced a customer-specific, enterprise-wide web portal for managing client software releases. The assignment involved taking new customer requirements, making architecture decisions and effort estimations, and prioritizing tasks.

Integrated several enterprise subsystems into the portal, namely Microsoft Exchange, Microsoft System Center Configuration Manager and other proprietary, customer-specific systems.

Corporate Intranet Portal with SharePoint

Being part of an on-site customer's team, I developed several features of a corporate intranet portal based on SharePoint 2010. My work included designing and implementing workflows, web parts, and SharePoint (web) services as well as writing configuration tasks and solution deployment.

SharePoint Forms and Tools Support

Being part of an in-house consulting team, I advised on and implemented custom InfoPath forms based on SharePoint and InfoPath forms services as well as custom-tailored support tools for emergency data support.

Since the team was directly assigned to C-level executives for quick information collection and retrieval assistance, the main focus was on innovative, non-standard solutions for forms and data collection tools that gave quick answers to "moving target" questions and problems.

REST Interface for Archive Services

Designed and implemented a REST-based API to query long-term backup archives via an existing, proprietary API provided by the backup system manufacturer.

The REST API was designed to support pluggable search features to extend the API without downtime.

Based on that REST API, I also developed several JavaScript plugins to existing intranet web pages to provide context-sensitive information about available backup data.

Unified Messenger Application

The customer developed an innovative messenger app and also wanted to integrate several existing messenger protocols of competitors to raise user acceptance. My task was to reverse engineer and reimplement the ICQ protocol and integrate my work as a plugin into the new app.

webXcerpt Information Manager

The customer developed an innovative solution for distributed web research and annotation collaboration, giving teams of web researchers the tools to make their research available to each other in real time and context-based within their web browsers.

My task was to design and develop the Internet Explorer browser integration.

Crawling Tool | nyx

Architected and implemented a tool for continuous crawling of network components such as switches and routers to trace IP addresses within a widespread infrastructure to find out about the physical location of compromised end devices. For this greenfield project, the foundations were laid in 2004 at LRZ München, Munich university's data center, constantly extended by many students and still in productive use till today.

Port Address Translator for Novell NetWare

Back in the days when Novell NetWare was still a thing, NetWare's focus was mainly on File and Print services, lacking many modern routers' TCP/IP features. I implemented a reverse NAT feature based on the NetWare NLM API to run public-facing services like SMTP and HTTP behind Novell NetWare-operated firewalls.


C#, HTML5, SQL, XML, JavaScript, Domain-specific Languages (DSLs), JavaScript 6, Bash Script, XLST, Visual Basic 6 (VB6), C++, SML, Java, Visual Basic, Visual Basic for Applications (VBA), TypeScript, CSS, C


.NET Core, Windows Presentation Foundation (WPF), ASP.NET Core, Mono, NHibernate, ASP.NET Web API, ASP.NET, ASP.NET MVC, ASP.NET MVC 4, .NET, Visual Studio Extensibility, Nano, Android SDK, ActiveX, Bootstrap, Windows Workflow Foundation


Office API, REST APIs, LINQ, PDFSharp, Windows Forms (WinForms), AMQP, PayPal API, jQuery, React, Visual Studio SDK, Apache Lucene, Java Servlets, WMI, OpenCV


Visual Studio 2019, Visual Studio Tools for Office (VSTO), EAGLE, NuGet, GitLab, Git, NGINX, Autofac, Novell NetWare, GitLab CI/CD, ANTLR 4, RabbitMQ, Wix Installer, Autodesk Fusion 360, MQTT, Microsoft Team Foundation Server, Wireshark, System Center Configuration Manager (SCCM), Apache Tomcat, Windows Installer, CMake, Microsoft InfoPath, Microsoft Silverlight


Model View ViewModel (MVVM), Microservices, REST


Linux, Docker, Raspberry Pi, Exchange Web Services, Eclipse, Embedded Linux, Oracle Database, Xamarin, SharePoint, Kubernetes, Azure, Web, SharePoint 2010, SharePoint 2007, Internet Explorer, Win32


JSON, NoSQL, MySQL, PostgreSQL, Neo4j, MongoDB, Oracle 11g, Microsoft SQL Server, Graph Databases, Redis, Elasticsearch, SQL Server Reporting Services (SSRS)


Computer Science, Constrained Application Protocol (CoAP), wyBuild, SSL, Windows Services, Code Generators, SNMP, TCP/IP, PDF, COM Interop, Customer Service, MS Ribbon, Microsoft Office SDK, SSL Certificates, Web Services, Active Listening, Industrial Internet of Things (IIoT), Embedded Systems, I2C, NLM, Microsoft Office, OMA Lightweight M2M, Sensor Networks, Ethernet, Reverse Engineering, Shell Extensions, ESP32, Windows Communication Foundation (WCF), Machine Learning, COM, MIB Files, Protocol Handlers, Tesseract

2000 - 2006

Master's Degree in Computer Science

Ludwig-Maximilans-Universität München - Munich, Germany

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