Sergey Fionov
Leading Software Engineer at AdGuard
Cyprus
Summary
🤩
Rockstar🎓
Top SchoolSergey Fionov is a seasoned C++ team lead with 17 years of experience building low-level, cross-platform systems and networking infrastructure, currently leading the development of AdGuard’s system-wide filtering engine. His background spans system programming for hosting (Ceph, QEMU, kernel modules), BGP and Flowspec implementations, and software-defined storage, giving him deep expertise in performance-sensitive, security-oriented engineering. Comfortable across the stack, he has also delivered frontend and backend solutions earlier in his career and contributed to private cloud projects. Based in Cyprus and educated in applied mathematics and system programming at MSU, Sergey blends rigorous academic grounding with hands-on leadership in production-critical C++ systems. An under-the-radar strength is his long-term focus on networking and OS-level tooling, which informs pragmatic design choices for robust cross-platform products.
17 years of coding experience
5 years of employment as a software developer
Specialist, Applied Mathematics/Computer Science/System Programming, Specialist, Applied Mathematics/Computer Science/System Programming at Московский Государственный Университет им. М.В. Ломоносова (МГУ)
Английский, Русский
Github Skills (137)
bug-tracker10
vpn-client10
async10
adblock10
blocking10
notification10
ads10
cross-platform10
advertising10
lwip10
open-source10
networking10
magisk10
vpn9
safari9
Programming languages (16)
Github contributions (5)
AdguardTeam/CoreLibs
Nov 2016 - Apr 2026
Core Adguard libraries
Contributions:2 reviews, 2 PRs, 873 comments in 9 years 6 months
wxwidgetscppazerothcoresecurityc-plus-plus
AdguardTeam/VerificationLibrary
Jun 2017 - Sep 2017
Certificates verification library
Contributions:33 commits, 4 PRs, 11 pushes in 2 months
verification-librarysecuritytlscertificatescertificate
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