Spencer Janssen
Senior Software Developer at MasterWord
Lincoln, Nebraska, United States
Summary
🤩
Rockstar🎓
Top SchoolSpencer Janssen is a Senior Software Developer based in Lincoln, Nebraska with 20 years of hands-on experience building reliable back-end systems. Currently at MasterWord since 2018, he brings deep practical expertise in performance tuning and algorithmic improvements, demonstrated by open-source contributions to Haskell's widely used bytestring library. His work on that project included bug fixes, adding unfoldr, and reworking sort to a counting sort implementation—changes that reflect a focus on both correctness and high-performance data processing. Prior roles at Ontellus further solidified his pragmatic engineering approach across production systems. Known for quietly improving core libraries rather than flashy front-end work, he combines long-term craftsmanship with an eye for measurable performance gains.
20 years of coding experience
2 years of employment as a software developer
University of Nebraska-Lincoln
Github Skills (8)
algorithm10
data-structures10
algorithms10
functional-programming10
haskell10
data-structure10
bytestring10
performance-optimization9
Programming languages (10)
Github contributions (5)
haskell/bytestring
Apr 2006 - Jul 2006
An efficient compact, immutable byte string type (both strict and lazy) suitable for binary or 8-bit character data.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:13 commits in 2 months
Contributions summary:Spencer primarily focused on improving the `bytestring` library, a Haskell package for efficient byte string manipulation. Their contributions include fixing bugs in existing functions like `foldr1` and `groupBy`. They also optimized the `sort` function by migrating to a counting sort algorithm, leading to performance improvements. Furthermore, they added the `unfoldr` function to both `ByteString` and `Char8`.
bytestring
spencerjanssen/btrfs-backup-sync
Jan 2019 - Jul 2020
Contributions:18 PRs, 63 pushes, 5 branches in 1 year 6 months
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