Résumé
Work, in order.
Developer tools at scale, from the Build Server Protocol to Bazel in JetBrains IDEs. Munich, Germany.
Justin Kaeser
Munich, Germany · Native German and English · justinkaeser.com · github.com/jastice · linkedin.com/in/justinkaeser
Summary
I work on developer systems where they stop working: at scale.
At JetBrains, I built and now lead the Bazel ecosystem. What started as a build-tool integration problem turned out to be an entry point into code at scale: large repositories, awkward project models, expensive indexing, questionable assumptions, and customers who notice quickly when tools stop being reliable. Most of my work happens somewhere between product, technical infrastructure, and direct customer pain.
Separately, I am testing a small energy-infrastructure venture for electric mobility in Kenya (Nenkima). It is early and pre-revenue.
JetBrains
Head of Bazel Ecosystem
Jan 2026 – Present
- Own product direction and business context for JetBrains' Bazel ecosystem, a strategic area at the intersection of build systems, IDE workflows, and code at scale.
- Treat Bazel not just as a plugin problem but as an entry point into understanding enterprise developer workflows, platform scalability, and trust in tooling.
- Work directly with major customers and developer-experience teams, using rollout problems, issue patterns, and real codebase behavior to set roadmap priorities and push cross-team platform work that would not have surfaced from aggregate metrics alone.
- Coordinate Bazel-related priorities with the Python, Go, and C++ ecosystems so the work stays compatible across teams, products, and customer workflows.
Team Lead, Bazel
Mar 2022 – Dec 2025
- Built Bazel support in IntelliJ from early exploration to enterprise rollout, after seeing the shift through customer work before it was a broader company priority. Took the new Bazel plugin from early access to general availability and into major-customer rollout in 2025. In roughly a year, it grew from zero to 30,000+ monthly active users in a niche whose overall market is probably not much larger than 100,000.
- Built and led a distributed multi-site team; hired, mentored, and developed engineers from intern level to de facto leadership roles.
- Worked directly with roughly 50 enterprise customers in the Bazel and code-at-scale space.
- Used customer codebases, issue patterns, and direct workflow observation to make product decisions and set cross-team technical priorities.
- Helped push IntelliJ platform support from projects that were merely large into codebases above 100,000 modules, where performance problems stop being theoretical very quickly.
- Established direct access to large customer repositories so we could debug real failures, validate workflows, and stop guessing.
- Helped create a new enterprise support motion around Bazel and large-codebase customers.
- Built recurring customer feedback loops and on-site engagement around events such as BazelCon and DPE Summit.
Customer Success Engineer (20%)
Nov 2021 – Dec 2023
- Worked directly with enterprise customers on build-tool and large-codebase problems, translating technical pain points into product direction, rollout support, and cross-team execution.
- Used customer conversations, issue patterns, and real codebases to surface the problems that matter before they show up cleanly in aggregate metrics.
- Introduced a system to track customer requests associated with product issues and notify the team about updates, allowing proactive customer updates.
Senior Software Developer, Scala
Jul 2016 – Apr 2022
- Co-designed the Build Server Protocol (BSP), now a standard integration layer between IDEs and build tools across much of the Scala ecosystem.
- Worked directly with build-tool authors and ecosystem maintainers to get BSP adopted in practice, not just specified.
- Delivered major improvements to sbt support in IntelliJ, including an integrated sbt shell and approximately 5x faster sync times.
- Improved BSP import performance and correctness in IntelliJ Scala: large-project import overhead, classpath correctness, library inference, and URI and path edge cases.
- Helped keep sbt and Bloop integration working through ecosystem breakage and dependency churn.
- Spoke at 30+ international conferences on Scala, Bazel, build systems, and developer experience.
Nenkima Ltd
Founder
Aug 2026 – Present, alongside JetBrains
- Founded a Kenyan company to test solar and charging infrastructure for electric motorbike taxis. Early stage and pre-revenue; no site is operating yet.
- Run it remotely from Munich, directing local field agents through bounded assignments whose results can be checked independently.
- Measure first, then model: sizing candidate Nairobi host sites from measured load (on-site loggers, swap logs, utility history) and modelled solar yield before committing any capital.
- Using Bazel-managed agent workflows (rules_agents) for research and operations.
1&1 Internet AG
Software Developer
Feb 2015 – Jun 2016
- Developed high-throughput data-processing systems for user authorization and recognition at Germany's largest email provider.
- Worked with Scala, Kafka, Redis, and Akka in production systems.
- Contributed Redis cluster functionality to the open-source Scredis client library.
Clueda AG
Software Engineer
Oct 2012 – Dec 2014
- Developed a real-time graph node-ranking algorithm and bulk data-processing tools with Hadoop.
- Helped drive adoption of Scala and Akka across the company.
- Improved development infrastructure with custom sbt plugins and TeamCity CI templates and test pipelines for more than 70 projects.
TrustYou
Software Developer
Apr 2010 – Oct 2012
- Backend and frontend web development, web crawling, and structured data extraction using J2EE, JavaScript, Node.js, and Hadoop.
ARITHNEA GmbH
Software Developer
Feb 2008 – Mar 2010
- Built automation for sitemap generation and CDN update workflows in the CacheControl product.
Open source and writing
- Build Server Protocol contributor: task notifications, property-based protocol testing, various fields and methods.
- rules_agents: an open-source experiment combining Bazel and agents to explore reliable, reproducible, and verifiable developer workflows.
- Mindless Midi: endless generative music in a browser tab. Claude writes the musical material at build time and it is checked in, so Bazel builds stay hermetic.
- ONI Material Graph: interactive explorer for material transformations in Oxygen Not Included, a static TypeScript app on a Bazel-pinned toolchain.
- JetBrains open source: IntelliJ Scala and Hirschgarten (the Bazel plugin).
- JetBrains blog: Integrating developer experiences (2019).
- JetBrains blog: Introducing the new Bazel plugin (2024).
Speaking and community
Speaker at 30+ international conferences since 2017, mostly on Scala, Bazel, build systems, and developer experience, including BazelCon, DPE Summit, IntelliJ Conference, Scale by the Bay, Scala Days, and Devoxx Poland. Built and supported community around JetBrains, Scala, and Bazel through meetups and networking events, and first established a repeatable process for hosting meetups at the JetBrains Munich office. All talks.
Education
- Ludwig-Maximilians-Universität Munich, Computational Linguistics
- Munich University of Applied Sciences, BSc Computer Science