Siim Kallas
Principal Software Engineer at Splunk
Tallinn, Harju County, Estonia
Summary
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Rockstar🎓
Top SchoolSiim Kallas is a Principal Software Engineer based in Tallinn with 12 years of experience building back-end systems, observability tooling, and performance-sensitive integrations. At Splunk he advances telemetry and tracing capabilities while previously shipping production services at companies like Sixfold and Plumbr. An active open-source contributor, he has extended OpenTelemetry across C++, JavaScript, and Nginx instrumentation and improved Rust SDL2 surface APIs, showing competence across languages and runtime boundaries. His work blends deep systems-level understanding (propagators, exporters, CI/CD for releases) with pragmatic engineering—automating test matrices and release builds to reduce friction to production. Colleagues describe him as someone who surfaces subtle runtime concerns early, such as correctly propagating context across async boundaries and capturing HTTP headers as tracing attributes. He holds a Computer Engineering background from the University of Tartu and brings a mix of hands-on coding and observability-driven architecture.
12 years of coding experience
8 years of employment as a software developer
Computer Engineering, Computer Engineering at University of Tartu
Stackoverflow
934reputation
59kreached
8answers
19questions
Github Skills (42)
javascript10
c-language10
back-end-development10
sdl10
distributed-tracing10
instrumentation10
binding10
api10
sdk10
jaeger10
opentelemetry10
nodejs10
rust10
nginx10
cprogramming-language10
Programming languages (16)
Github contributions (5)
open-telemetry/opentelemetry-cpp-contrib
Feb 2021 - Jul 2022
Role in this project:
Back-end & DevOps Engineer
Back-end & DevOps EngineerContributions:75 reviews, 14 commits, 64 PRs in 1 year 5 months
Contributions summary:Siim contributed significantly to the OpenTelemetry instrumentation for the Nginx web server, introducing features like custom attribute support. They implemented the core logic for tracing HTTP requests within Nginx, including context propagation and span creation. Furthermore, they worked on the CI/CD pipeline by adding a test matrix and release build configurations, demonstrating a focus on automation and deployment.
open-telemetry/opentelemetry-js
Mar 2021 - Nov 2022
OpenTelemetry JavaScript Client
Role in this project:Backend Developer
Backend DeveloperContributions:54 reviews, 11 commits, 18 PRs in 1 year 8 months
Contributions summary:Siim primarily contributed to the OpenTelemetry JavaScript client, focusing on improving HTTP instrumentation. They fixed issues in how the net and HTTP instrumentations link, added the functionality to capture HTTP headers as span attributes. The user also made several refactorings to improve the metric aggregation and data models. Furthermore, they addressed issues related to instrumentation and metrics, including bug fixes and enhancements.
apijavascript-clientjavascripttelemetryotel
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