Eirik Tsarpalis
Principal Software Engineer, .NET Libraries at Microsoft
London, England, United Kingdom
Summary
🤩
Rockstar🎓
Top SchoolEirik Tsarpalis is a Principal Software Engineer at Microsoft with over a decade of experience building high-performance .NET libraries, distributed systems, and industrial R&D platforms. He focuses on API design, performance engineering, and functional programming, bringing deep expertise in System.Text.Json, reflection-based schema generation, and AOT compatibility. At Microsoft he helps maintain the Base Class Libraries and has contributed notable fixes and benchmarks across dotnet/runtime and dotnet/performance, improving process handling and serialization performance. His open-source work includes adding Async.Choice to the F# core library and enhancing the widely used dotnet/extensions and Semantic Kernel projects to better support structured output for LLM integration. Prior roles at Walmart Labs and Nessos grounded him in production migration to .NET Core, event-sourced microservices, and distributed compute research (MBrace). Trained in mathematics and computer science at Cambridge and Athens, he blends rigorous theoretical grounding with practical engineering that surfaces in subtle improvements to telemetry, logging, and API ergonomics.
13 years of coding experience
5 years of employment as a software developer
BSc Mathematics, BSc Mathematics at National & Kapodistrian University of AthensCertificate of Postgraduate Studies Computer Science, Certificate of Postgraduate Studies Computer Science at University of Cambridge
Greek, English
Github Skills (59)
asynchronous10
arcgisruntime10
unit-testing10
nuget10
markdown10
reflection10
benchmark10
runtimes10
package-management10
json-schema10
multithreading10
async10
net10
process-management10
dotnet10
Programming languages (9)
Github contributions (5)
fsprojects/FSharp.Formatting
Jul 2014 - Jul 2020
F# tools for generating documentation (Markdown processor and F# code formatter)
Role in this project:
Full-stack Developer
Full-stack DeveloperContributions:86 commits, 14 PRs, 16 pushes in 6 years 1 month
Contributions summary:Eirik primarily contributed to the F# code formatting and documentation generation tools within the repository. They implemented features like anchor generation for HTML headings and improved comment parsing in the code formatter. Furthermore, the user updated build scripts and dependencies, and made adjustments to Razor engine integration, and overall website generation process. They also addressed several bugs and refactored code to maintain the project's functionality.
fsharpcode-formatterformattermarkdown-processormarkdown
dotnet/runtime
Jul 2019 - Jan 2023
.NET is a cross-platform runtime for cloud, mobile, desktop, and IoT apps.
Role in this project:Back-end Developer & Test Automation Engineer
Back-end Developer & Test Automation EngineerContributions:4217 reviews, 374 commits, 1106 PRs in 3 years 7 months
Contributions summary:Eirik made significant contributions to the .NET runtime repository, primarily focused on enhancing the process management capabilities of the .NET platform. Their work involved implementing a fix for an issue in `Process.WaitForExitAsync`, and included refactoring and testing code related to thread-safety within various parts of the runtime's process handling. This included addressing issues that pertained to correct stream handling and overall code improvements. The user's efforts also involved enhancing and testing code related to the Json serialization.
dotnetruntimelinuxcsharpxamarin
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