Josef Vlach
Contractor Scala Developer at HM Revenue & Customs
London, England, United Kingdom
Summary
👤
Senior🎓
Top SchoolJosef Vlach is a contractor Scala developer based in London with 12 years of experience building reliable backend systems and migrating legacy services into modern microservice architectures. A functional-programming evangelist, he brings deep practical knowledge of Scala, Cats, Play Framework and type-safe patterns—often catching subtle bugs by raising type safety and compiler rigor. He has applied these skills across public sector and finance (HMRC, Barclays) and in gaming and startups, leading backend engineering, CI/CD and DevOps automation for high-availability services. An active open-source contributor, Josef has improved parsing and header handling in the prominent http4s Scala HTTP library, reflecting a focus on clean, idiomatic APIs and robust parsing logic. Notably, his background in Haskell and experience introducing Tagged types and compile-time checks have repeatedly surfaced latent defects and improved long-term maintainability.
12 years of coding experience
10 years of employment as a software developer
Bachelor's Degree, Software Engineering, Bachelor's Degree, Software Engineering at Czech Technical University in PragueMaster's Degree, University of West Bohemia, Master's Degree, University of West Bohemia at University of West Bohemia, Pilsen
Czech, English
Stackoverflow
379reputation
66kreached
8answers
0questions
Github Skills (13)
typer10
scala10
cat10
http10
parsing10
headers10
parse10
top-level10
fs8
json6
scalatest6
playframework6
environment-variables6
Programming languages (12)
Github contributions (5)
http4s/http4s
Feb 2021 - Mar 2021
A minimal, idiomatic Scala interface for HTTP
Role in this project:
Back-end Developer
Back-end DeveloperContributions:4 reviews, 33 commits, 15 PRs in 23 days
Contributions summary:Josef primarily contributed to refactoring and cleaning up various header implementations, including `Accept-Charset`, `Accept`, `Access-Control-Allow-Headers`, `Accept-Language`, `Content-Language`, `Cookie`, `Cache-Control`, `WWW-Authenticate`, `X-Forwarded-For`, `Proxy-Authenticate`, `Forwarded`, `Access-Control-Expose-Headers`, `Link`, `Strict-Transport-Security`, `Transfer-Encoding`, `User-Agent`, and related parsing logic. These changes involved code cleanup, optimization, and migration to new header implementations. The user also touched upon related testing files, and updated the parser.
idiomatichttp-clientscalafs2typelevel
VlachJosef/println-debugger
Jun 2017 - Feb 2024
Contributions:80 pushes, 2 branches in 6 years 9 months
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