Li Haoyi

Databricks

• Sped up core developer workflows (compiling Scala, local testing, CI validation, configuring deployments, ...) by 5-10x, reducing minutes- to tens-of-minutes-long workflows to a few seconds
• Implemented a 50x faster compiler and an IntelliJ IDE plugin for the Jsonnet configuration language
• Developed an elastic "Dev Box" service that provides on-demand, one-click cloud development environments, doubling the speed of dev workflows while minimizing costs by shutting down when not in use
• Led the Devtools prioritization process: surveying engineers on their pain points, aggregating feedback, and planning projects to improve things. Increased the average self-reported happiness score from 3.1 to 4.0/5.0
• Introduced many development practices to the org: JVM profiling, structured error logging, code auto-formatting
• Ran weekly tech talks with internal and external speakers to share knowledge, with several dozen talks given so far

Dropbox

• Built Python/Javascript static analysis tools, speeding work while preserving quality, preventing 50+ defects a week
• Rolled out an improved development workflow, reducing edit-refresh latency by 3x for Python and Coffeescript
• Led a team of 2-3 to destroy flaky tests; reduced the number of builds failing due to flaky tests from about 10% to 1%
• Helped manage our CI system comprising >3000 CI machines
• Mentored an intern completing a successful project (test quarantine) in his 12 weeks here
• Set up Selenium tests (> 300 CI machines) & got them adopted. Reduced bugs reaching production by 5-10 a week
• Modularized our >100,000 lines of Coffeescript, from a 'cat em all' build system to Require.js modules
• Built an auto-packager using machine learning to reduce the number of Javascript downloads by 200ish per page
• Performance improvements for most common pages, including speeding up the home page by 6x

Mill

Ammonite

FastParse

Scala.js

Google Summer of Code

• Mentored Abhishek Kumar, working on performance, usability and Windows-support for Ammonite's scripts
• Mentored Vladimir Polushin, who extended Fastparse's string-parsing to support parsing binary and streaming input
• Mentored Laszlo Mero, who first implemented script-running support for the Ammonite REPL