Josselin Costanzi
Senior Software Engineer at Robinhood
Seattle, Washington, United States
Summary
🤩
Rockstar🎓
Top SchoolJosselin Costanzi is a Senior Software Engineer with 12 years of experience building cloud-native and low-level systems, currently based in Seattle and working at Robinhood after a significant tenure at AWS. He specializes in Kubernetes, distributed systems, and DevOps automation—at AWS he led initiatives that made EKS partition-agnostic and slashed critical update and deployment times by up to 90% and 60% respectively. Comfortable across the stack, he has a background in embedded systems and kernel development as well as stream processing with Kafka, Go, gRPC and Kubernetes. An advocate for security and correctness, he discovered and helped remediate a Go http2 CVE and routinely performed threat-model reviews across EKS teams. He contributes to the Go project, improving core packages like encoding/base64 with correctness fixes, performance optimizations and benchmark tests—showing attention to both micro-optimizations and production impact. Trained as an electrical and electronics engineer in France, he blends low-level rigor with cloud-scale operational engineering.
12 years of coding experience
8 years of employment as a software developer
Master of Engineering (M.Eng.), Electrical and Electronics Engineering, Master of Engineering (M.Eng.), Electrical and Electronics Engineering at Institut national des Sciences appliquées de LyonDiplôme universitaire de technologie, Electrical and Electronics Engineering, Diplôme universitaire de technologie, Electrical and Electronics Engineering at IUT de Grenoble
Github Skills (17)
programming-language10
go10
golang10
algorithm9
code-optimization9
algorithms9
optimisation9
numerical-optimization9
optimization9
performance-tuning8
performance-analysis8
performance-measurement8
performance-analytics8
performance-monitor8
testing8
Programming languages (9)
Github contributions (5)
golang/go
Jan 2017 - May 2017
The Go programming language
Role in this project:
Back-end Developer
Back-end DeveloperContributions:4 comments, 6 issues in 3 months
Contributions summary:Josselin focused on improving the `encoding/base64` package within the Go programming language repository. They addressed bugs related to incorrect index reporting during decoding and implemented restrictions on alphabet and padding characters. Furthermore, the user optimized the `DecodeString` function for performance gains and contributed optimizations using specialized methods, demonstrating a focus on code efficiency and correctness. They also added benchmark tests to measure the improvements.
golanggopluscompilerprogramming-languageinterpreter
josselin-c/amazon-eks-pod-identity-webhook
Feb 2020 - Oct 2020
Amazon EKS Pod Identity Webhook
Contributions:24 pushes, 2 branches, 1 tag in 8 months
amazon-eksamazonpod-identityekswebhook
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