Konstantin Tsoy - Software Engineer at Meta

Konstantin Tsoy

Software Engineer at Meta

Seattle, Washington, United States

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Summary

🤩

Rockstar

🎓

Top School

Konstantin Tsoy is a seasoned software engineer with a decade of experience specializing in computer networking and systems-level C++ development, currently building networking infrastructure at Meta in Seattle. He has a strong track record at networking-focused companies like F5 and Tempered Networks and has contributed significant fixes and features to high-profile open-source projects such as Facebook's proxygen, mvfst (QUIC), hhvm, and folly. His work spans protocol-level bug fixes, partial reliability and retransmission handling, and cross-platform UDP/socket enhancements—including bringing Windows-specific optimizations like recvmmsg/WSASendMsg and GSO support. Known for digging into race conditions and low-level performance bottlenecks, he blends rigorous testing with pragmatic engineering to harden transport and HTTP stacks. With a master’s in Information Security, he brings both systems expertise and security-aware thinking to complex distributed networking problems.

10 years of coding experience

7 years of employment as a software developer

Master's degree Information Security, Master's degree Information Security at Tomsk State University of Control Systems and Radioelectronics

English, Russian

Github Skills (26)

udp10

c-language10

multithreading10

testing10

windows10

hacking10

http10

networking10

hhvm10

network-programming10

php10

socket10

network-protocol10

quic10

cprogramming-language10

Programming languages (4)

C++RustCPython

Github contributions (5)

facebook/mvfst

Apr 2019 - Jan 2023

An implementation of the QUIC transport protocol.

Role in this project:

Back-end Developer

Contributions:95 commits, 2 PRs, 1 push in 3 years 9 months

Contributions summary:Konstantin primarily focused on addressing a race condition within the QUIC transport protocol implementation. They identified and resolved a bug related to the retransmission buffer handling during ACK frame processing and min data frame (skip) processing. The user modified the stream state handlers to ensure the retransmission buffer correctly corresponds to stream data. They also added test cases to cover and validate the changes.

quichttp3protocolsctptransport

facebook/proxygen

May 2019 - Oct 2022

A collection of C++ HTTP libraries including an easy to use HTTP server.

Role in this project:

Back-end Developer

Contributions:51 commits, 3 PRs, 4 pushes in 3 years 6 months

Contributions summary:Konstantin primarily focused on back-end development, specifically enhancing the `proxygen` HTTP library. Their contributions involved modifying the HTTPCodec interface and implementing new features for partially reliable body handling. Furthermore, the user worked on incorporating partial reliability flags within the HTTPMessage class and making changes to the HTTPTransaction and HTTPTransactionHandler interfaces to facilitate these features. The work included changes to the HQSession and HQStreamTransport to implement the features.

http-serverc-plus-pluscppuse-http

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