Csaba Keri, Full-stack Developer in Zurich, Switzerland
Csaba Keri

Full-stack Developer in Zurich, Switzerland

Member since May 29, 2020
Csaba is a full-stack developer who's been working with C# and SQL since 2001 and as an architect since 2015. Csaba is comfortable working with companies of all sizes using both the Waterfall and Agile methodologies and has experience in banking & finance (ten years), aviation (six years), and TV/radio stations (four years). Csaba also excels at database & application architecture planning, implementation, quality assurance, data transformation (ETL), and performance optimization.
Csaba is now available for hire


  • Freelance (Smaller Projects)
    AWS, Python 3, VB, VB.NET, WCF Web Services, Encryption, Decompilation
  • KPMG
    API Integration, Fintech, Full-stack, Regression Testing, Best Practices...
  • UBS
    Fintech, Full-stack, SQL Server Integration Services (SSIS), Angular...



Zurich, Switzerland



Preferred Environment

Kanban, Scrum, Web MVC, C#.NET, SQL, Slack, Visual Studio, Windows

The most amazing...

...thing I've developed is the entire application for a real shop, which covered all possible activities: billing, storage maintenance, and a lots of reports.


  • Developer

    2020 - PRESENT
    Freelance (Smaller Projects)
    • Ported a legacy VB6 application to Windows 7 GUI/OCX/DLL.
    • Created a C# application to interact with other GUI applications through WCF calls and duplex WCF proxies.
    • Developed an AWS Lambda function for user authentication, key encryption, and custom logic with Python 3.
    Technologies: AWS, Python 3, VB, VB.NET, WCF Web Services, Encryption, Decompilation
  • Assistant Director | Senior Software Developer | Engineer

    2017 - 2020
    • Planned, implemented, maintained, and fixed the rules and core functionalities of a multi-shore tax reporting application with more than 400 calculation rules and a distributed architecture with more than 100 parallel calculation threads.
    • Managed and maintained the Docker environment and web UIs based on Razor and Angular.
    • Maintained the infrastructure and the Windows and SQL server by implementing health monitoring and cleanup processes and optimizing resource usage.
    Technologies: API Integration, Fintech, Full-stack, Regression Testing, Best Practices, MVC Razor, ASP.NET, ASP.NET MVC, APIs, .NET, Server Infrastructure, .NET Core, Load Testing, App Infrastructure, Code Architecture, Requirements Analysis, Data Loading, Microsoft SQL Server, Parallel Programming, Kanban, Scrum, Docker, Angular, C#.NET, Azure, jQuery, JavaScript, HTML5, CSS3, Bootstrap UI, Architecture, Bug Fixes
  • Associate Director

    2016 - 2017
    • Planned out the architecture, development, change management, code reviews, and bug fixes of an internal business application with a web app, ClickOnce, and Windows service components.
    • Worked on complex business functions, forecasting, nightly calculations, and client report generation regarding the performance of several financial organizations based on the data provided by them.
    • Continuously communicated with the business users which included requirement gathering, release planning, training, coaching, and mentoring of an apprentice.
    Technologies: Fintech, Full-stack, SQL Server Integration Services (SSIS), Angular, Regression Testing, Best Practices, WCF Web Services, .NET, Agile, JavaScript, Banking & Finance, Business Reporting, Requirements Analysis, Scrum, Microsoft SQL Server, C#, DevExpress, DevOps
  • Senior Architect

    2014 - 2016
    Infomatix Ltd.
    • Led two Scrum development teams, ensured deadlines were kept, and provided technical support for all team members.
    • Extended the TIBCO Spotfire data visualization application with enhancements, extensions, and management tools.
    • Reviewed the code, designed the software architecture, trained, ensured quality, and found and investigated new directions and technologies.
    • Optimized SQL, Hadoop/Hive queries, and C# code resulting in 30-200% performance improvement.
    Technologies: API Integration, Fintech, Full-stack, Regression Testing, Best Practices, WCF Web Services, ASP.NET MVC, ASP.NET, jQuery, Web MVC, MVC Razor, APIs, .NET, Quality Assurance (QA), Kanban, Scrum, Jira, Microsoft SQL Server, C#.NET, Financial Reporting, Business Intelligence (BI), Spotfire
  • Lead Developer

    2013 - 2014
    • Led a team of four developers that designed and built a distributed n-tier architecture multimedia content provider system like Netflix; it was used in multiple countries with multiple languages and had a central management system on 100+ servers.
    • Planned, designed, and developed a distributed web app for a hardware store. The main functionalities of the app were to sell custom products to suppliers and to generate and print statistics.
    • Optimized SQL queries and C# code, resulting in 30-50% performance improvement.
    Technologies: API Integration, Fintech, Full-stack, Regression Testing, Best Practices, WCF Web Services, APIs, MVC Razor, jQuery UI, ASP.NET MVC 6, ASP.NET, .NET, jQuery, JavaScript, HTML, Microsoft SQL Server, C#.NET
  • Senior Software Engineer

    2012 - 2013
    EPAM Systems
    • Designed and developed multiple internal web apps to support the HR and resource planning processes of my team.
    • Took part in the first round of a Google hackathon and created a robot that had to occupy areas based on the rule book.
    • Optimized SQL queries and C# code resulting in 10-80% performance improvement.
    Technologies: Full-stack, Best Practices, WCF Web Services, jQuery, ASP.NET Razor, ASP.NET MVC, ASP.NET, .NET, Test-driven Development (TDD), Business Requirements, Requirements Analysis, Scrum, SVG, Oracle, Microsoft SQL Server, JavaScript, MVC Razor, C#.NET
  • Business Analyst | Architect

    2004 - 2013
    • Developed a complete application for a company with two shops and 25 employees (sellers) together. The app covered all the needs of the shop. From 2011, it was integrated with the webshop partially (both used the same storage).
    • Implemented the main functions of sales, billing, automated orders, storage management, and alerts.
    • Developed various forms of reporting, including automated reports, customizable reports, and time-focused reports (daily, bi-weekly, monthly, and yearly).
    • Created a business recovery plan which included graceful degradation; also owned performance monitoring.
    Technologies: PostgreSQL, MySQL
  • Senior Software Developer

    2007 - 2012
    Grape Solutions Ltd.
    • Planned and implemented the base site engine and web check-in, additional services, passenger data; Wizzair.com version 1 ( 2007- 2010, not 100%). The engine was written in 40 hours, based on ASP, XML, XSLT, fully dynamic and recursive.
    • Planned and developed the new site, which has been live since June 2012; Wizzair.com version 2 (2011-2012). The site was completely rewritten based on a mandatory third-party DLL library.
    • Developed and planned the validation—processing, transforming of CSV data, and saving into SQL 2005 with SSIS for an American bank. It loaded 2-4GB every night with the constraint that during the load the old must be constantly accessible.
    • Implemented the MS Access migration to SQL Server which included planning and creating an SQL Server database and loading data from MS Access into it.
    • Developed a web-based insurance agent administration system for agent performance and commission calculation, approval system with a client-side grid containing dynamically defined calculations.
    • Created the VAT refund system for Singapore customs in airports. The WPF UI contained all VAT related data with the possibility of approval/denial of the VAT refund by the customs..
    • Optimized SQL databases, queries, and C# code resulting in 20-120% performance improvement for several applications and environments to be able to serve the load, persist data, and resist DDOS attacks.
    Technologies: API Integration, Fintech, Full-stack, WCF Web Services, jQuery, MVC Razor, ASP.NET MVC, ASP.NET, APIs, .NET, DDoS, Outlook Add-ons, Visual Basic for Applications (VBA), Performance Analysis, Optimization, Finance, Microsoft Access, ETL, Scripting, XSLT, XML, SQL Server Reporting Services (SSRS), SQL Server Integration Services (SSIS), OLAP, Windows Presentation Foundation (WPF), Website Performance, Load Testing, Clustering, Dynamic Load Balancing, Aviation, Perl, CSS, HTML, JavaScript, Microsoft SQL Server, C#.NET
  • Contract Developer

    2001 - 2007
    • Planned and developed a complete radio station site. The site had a complex management page with scheduling and other services.
    • Planned, developed, and tested a modular portal system as an alternative to SharePoint 2003, with a workflow engine. Features are document, permission, user, and extension management. New modules can be loaded at any time without restarting the portal.
    • Integrated different parts of a mobile phone-based payment system using BizTalk.
    • Installed a high availability MS SQL, BizTalk, and IIS cluster with a port logging application for one of the biggest Hungarian banks.
    • Created a system test plan for a newly developed system of a mobile telecommunications company with Mercury TestDirector.
    • Developed a real-time factory controlling system with time-critical response times for a laundry business.
    Technologies: Full-stack, jQuery, Regression Testing, Best Practices, WCF Web Services, MVC Razor, ASP.NET MVC, ASP.NET Web Forms, ASP.NET, APIs, .NET, Requirements & Specifications, Load Testing, Requirements Analysis, Waterfall Methodology, Kanban, Scrum, Load Balancers, Orchestration, Integration, Eclipse IDE, Java, Oracle, Clustering, Web Services, ASMX, ASPX, CSS, HTML, JavaScript, C#.NET, Microsoft SQL Server, BizTalk
  • Software Developer

    2000 - 2001
    Nextra Hungary Ltd.
    • Planned, created, and tested a product with IE Administration Kit. It could install a modem on Windows, connect to a server, guide the user through the registration, and at the end, downloaded a configuration and configured the modem for web surfing.
    • Developed internal Nextra web pages based on SQL Server, Visual Basic, or ASP/HTML.
    • Developed an internal app to support the company processes.
    Technologies: Full-stack, APIs, SQL, Internet Explorer Adminsitration Kit, ASP, Visual Basic 6 (VB6), JavaScript, Excel VBA


  • Fully Recursive Web Engine

    With another developer, we made a recursive engine that could build and serve web pages based on a recursive XML declaration with its own nodes, page processing, and building engine, which filled the sites with multilingual content (taken from the disk, session, and SQL server).

    The engine could implement a graceful degradation and keep the core functionality even if all the auxiliary components failed. The logic contained a continuous performance monitoring system to detect the bottlenecks and DDOS attacks immediately.

  • Multi-shore Tax Reporting

    A C# and SQL server-based, heavily parallel, distributed application with very complicated calculations on a large amount of data (100,000+ data points/customer) with strong performance expectations (regarding the number of the calculations/hour).

    My contributions were the data loading (extract, transform, load), the parallel logic in the business layer, several rules, and performance optimization with remarkable results. I was also responsible for the quality assurance of the imported data and the detection of inconsistencies, missing data points, and everything else.

    I took part in the core architecture planning and was the only person responsible for the core application part—which formed the basis for the customized app features.

    I also maintained the (virtual) hardware environment (including the Windows, SQL servers, and Docker). I kept the application stable and alive at any circumstances (because of the strict legal delivery deadlines).

    I also created an end-to-end testing tool, which was able to compare any parts of the reports and find all the differences, regressions, unforeseen data constellations, and calculation errors with a speed of 3,000+ reports/hour.

  • Leading the Back-end Development at an On-demand TV Channel

    I was the head of back-end development on an on-demand TV channel with monthly subscription fee. My responsibility was to ensure bug-free and architecturally optimal code and manage the releases twice a week in more than 15 countries on more than 50 serves. Besides being a lead, I took part in the code development on the back-end side and the client side as well—I wrote a client for a set-top box in Javascript. I took part in the weekly planning meetings and the management to have the best roadmap and deliver the highest possible business value from week to week. I was also responsible for the back-end API, which was used by all of the clients (Win Mobile, iOS, Android, and web browsers).


  • Languages

    SQL, C#.NET, JavaScript, XML, C#, ASP.NET Razor, Excel VBA, HTML, CSS, XSLT, Python 3, VB, VB.NET, HTML5, CSS3, Visual Basic 6 (VB6), Perl, Visual Basic for Applications (VBA)
  • Frameworks

    ASMX, MVC Razor, .NET Core, .NET, ASP.NET, ASP.NET Web Forms, ASP.NET MVC, ASP.NET MVC 6, ASP, Windows Presentation Foundation (WPF), Angular
  • Libraries/APIs

    REST APIs, ASPX, API Development, jQuery UI, jQuery
  • Tools

    Visual Studio, Jira, Slack, Eclipse IDE, Microsoft Access, Spotfire
  • Paradigms

    Scrum, Testing, Unit Testing, Agile, E2E Testing, Best Practices, Continuous Integration (CI), REST, MVC Design, Kanban, Requirements Analysis, Load Testing, Clean Code, Management, DevOps, OLAP, ETL, DDoS, Business Intelligence (BI), Test-driven Development (TDD), Parallel Programming
  • Storage

    Databases, SQL Performance, Microsoft SQL Server, PostgreSQL, MySQL, SQL Server Integration Services (SSIS), SQL Server Reporting Services (SSRS), Oracle 10g
  • Other

    Architecture, Software Development, Business Logic, Code Architecture, Performance Tuning, Web Services, Waterfall Methodology, APIs, Regression Testing, Full-stack, Fintech, Bug Fixes, Web MVC, Data Loading, Integration, Requirements & Specifications, High Code Quality, TFS Work Items, Financial Reporting, Website Performance, Scripting, Optimization, Performance Analysis, Quality Assurance (QA), App Infrastructure, Leadership, Team Leadership, Delivery Management, API Integration, Decompilation, Bootstrap UI, Group Management, Server Infrastructure, Infrastructure Monitoring, Internet Explorer Adminsitration Kit, BizTalk, Clustering, Orchestration, Load Balancers, Aviation, Dynamic Load Balancing, Finance, Outlook Add-ons, SVG, Business Requirements, Business Reporting, WCF Web Services, AWS, Encryption, DevExpress
  • Platforms

    Windows, Docker, Oracle, Azure
  • Industry Expertise

    Banking & Finance


  • Bachelor's degree in International Trade
    1998 - 2002
    High School for Foreign Trade & Economics - Budapest, Hungary
  • Master's degree in Computer Science
    1995 - 2000
    Technical University - Budapest, Hungary

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