Jan Havlíček
Development Lead at Seznam.cz, a.s
Brno, South Moravia, Czechia
Summary
🤩
Rockstar🎓
Top SchoolJan Havlíček is a development lead with 12 years of experience architecting and delivering high-throughput backend systems at Seznam.cz, where he currently guides 60–70 engineers across Mapy.cz and Email.cz. He combines hands-on C++, Python and cloud-native expertise (Docker, Kubernetes) with team leadership, hiring, budgeting and company-wide technical decision-making. Previously he led a smaller Mapy.cz team building distributed image processing pipelines, data import workflows and backend components serving thousands of requests per second. As an open-source contributor he has improved reliability of the popular ClosedXML .NET library by reimplementing Excel formula semantics and expanding array-formula support, demonstrating attention to correctness and deep familiarity with legacy calculation engines. He holds an Mgr. in Computer Science from Masaryk University and pairs academic grounding with practical production experience.
12 years of coding experience
2 years of employment as a software developer
Master (Mgr.), Computer Science, Master (Mgr.), Computer Science at Masaryk university
English
Github Skills (10)
net10
asp-net10
formula10
dotnet10
csharp10
parsing10
parse10
formulas10
dotnet-core10
test-automation10
Programming languages (10)
Github contributions (5)
ClosedXML/ClosedXML
Jul 2022 - Jan 2023
ClosedXML is a .NET library for reading, manipulating and writing Excel 2007+ (.xlsx, .xlsm) files. It aims to provide an intuitive and user-friendly interface to dealing with the underlying OpenXML API.
Role in this project:
Back-end Developer & Test Automation Engineer
Back-end Developer & Test Automation EngineerContributions:21 releases, 49 reviews, 246 commits in 6 months
Contributions summary:Jan primarily contributed to improving the codebase's reliability and functionality by addressing issues related to formula parsing and evaluation. They reimplemented several legacy calculation engine functions, including ISBLANK, ISERR, ISERROR, ISEVEN, ISODD, ISTEXT, ISNUMBER, ISNA, ISNONTEXT, and N, ensuring closer adherence to Excel's behavior. Furthermore, they added and improved tests for the updated functions, and expanded the functionality to support array formulas and data table.
xlsxapidotnetnet-libraryclosedxml
jahav/dataisland
Aug 2024 - Oct 2024
Contributions:2 releases, 36 PRs, 119 pushes in 1 month
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