John Szumski
Senior Staff Software Engineer at Cash App
Richmond, Virginia, United States
Summary
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Rockstar🎓
Top SchoolJohn Szumski is a Senior Staff Software Engineer with 13 years of experience building mobile platforms, currently driving engineering at Cash App from Richmond, VA. He combines hands-on iOS/Swift expertise with leadership experience from roles at Twitter and Capital One, focusing on reliable, production-ready mobile systems. An active open-source contributor, he has improved Swift tooling and protocol buffer implementations—contributing notable fixes to projects like square/wire and the widely used SwiftLint. Known for sharpening code quality and edge-case robustness, he brings a pragmatic engineer-manager perspective that balances shipping features with maintainability.
13 years of coding experience
12 years of employment as a software developer
BS, Computer Science, BS, Computer Science at University of Virginia
Stackoverflow
7,440reputation
381kreached
198answers
1question
objective-c
top-5%
uitableview
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ios
top-1%
Github Skills (23)
ios10
static-analysis10
protocol-buffers10
decode10
software-quality10
decoding10
computer-engineering10
encoding10
linting10
encode10
swift10
testing9
objective-c9
uitableview9
automations8
Programming languages (9)
Github contributions (5)
realm/SwiftLint
Mar 2018 - Nov 2022
A tool to enforce Swift style and conventions.
Role in this project:
Software Engineer (Focus on Code Quality)
Software Engineer (Focus on Code Quality)Contributions:2 reviews, 9 commits, 6 PRs in 4 years 8 months
Contributions summary:John primarily contributed to the improvement and maintenance of the SwiftLint project, focusing on code quality and linting rules. Their work involved fixing typos, improving autocorrect behavior with preprocessor macros, and adding new triggers for existing rules. The user also made modifications to existing rules, adding checks, and correcting edge cases, thus enhancing the functionality and robustness of the tool. These improvements included making adjustments to existing rules to avoid unintended behavior.
linterswift-package-managerbazellintingcode-quality
square/wire
Mar 2023 - Nov 2024
gRPC and protocol buffers for Android, Kotlin, Swift and Java.
Role in this project:Back-end Developer
Back-end DeveloperContributions:19 reviews, 8 PRs, 10 pushes in 1 year 8 months
Contributions summary:John primarily worked on improving the encoding and decoding of Protocol Buffer messages in Swift, specifically addressing issues with proto3 default values and size-delimited message collections. They also fixed a bug related to the encoding of proto3 messages with omitted values. Furthermore, the user added the ability to encode and decode size delimited message collections. These changes involved modifications to `ProtoEncoder`, `ProtoDecoder`, and `ProtoWriter` within the `wire-runtime-swift` module.
protocol-buffersprotobufgrpcandroidbuffers
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