Jakub Gieryluk senior software engineer jakub.gieryluk.net/cv
last updated 2021.04

• JavaScript (ES6/ESM)
• HTML5
• Preact
• Redux
• webpack
• Babel
• WebPageTest
• Chrome DevTools perf panel
• Kibana
• NodeJS
• Git

Improving loading time of Dailymotion video player (350MM MAU, Alexa top-300 traffic site globally).

• Researched & documented player internals and optimization opportunities
• Prioritized the findings & created performance roadmaps
• Defined, implemented, shipped & documented RUM performance metrics
• Built & documented performance RUM dashboards
• Improved the codebase to allow for better profiling & performance analysis
• Shipped multiple perf optimizations
  • Reshuffled JavaScript loading priorities and preloaded critical subresources
    • 3x ~10% load time improvements
  • Reduced critical JS bundle size by ~15% (200 kB js.min, 50 kB gzipped) by minimally changing browser support level, dropping dead code and heavy dependencies
    • JS load time improved by ~20% at 90th percentile
• Mentored 5 team members on performance subjects
• Advised on cross-team performance missions

• Documented team processes that were poorly defined and mostly ad-hoc
  • Defined data-driven organization-wide browser support policy
  • Re-defined localization process & tooling
  • Wrote guides on adding & validating telemetry, and on investigating spikes
• Contributed to several post-mortem investigations & took actions to prevent issues from re-occurring
  • Improved production deployment checklist
  • Improved release monitoring dashboards
  • Led the efforts to increase logs retention (5d -> 21d) to improve regressions investigations
• Made automated test suite reliable by moving off SauceLabs to local headless Chrome in Docker

• Android
• Java
• Android Studio
• Material Design
• RxJava
• Dagger
• JUnit
• Robolectric
• Git

Rewrite of hybrid Cordova app as a native Android app (2-dev team) for better UX. Features delivered:

• Seamless user migration from the hybrid Cordova app
• Localization & internationalization code, processes & tooling
• "Add to calendar" and share-related code
• Parts of the UI of the app

• JavaScript
• Angular.js
• HTML5
• CSS3
• Ionic
• Cordova
• Android
• Karma
• Git
• Jenkins
• Chrome DevTools
• NodeJS
• HTTPS
• Apache
• bash

• Rebuilt from scratch a ~2MM MAU travel app (Android & web) using Ionic/Cordova/Angular.js (3 dev team)
• Google Play Store user rating soared to 4.5

• Wrote robust front-end code, automated tests (~70% coverage), specs, tooling; did extensive code reviews
• Refined features and APIs with product owner, backend and iOS teams
• Volunteered in security discussions & rotated in scrum master role
• Maintained legacy app (bug fixes, code reviews, perf optimizations)

• Debugged & resolved several critical issues with Android app (some users unable to update / log in / connect over HTTPS)
• Led the migration from the legacy web app in a smooth and backward-compatible way
• Set up a robust, automated build infrastructure on top of Jenkins, including a HipChat bot
• Authentication, seamless account activation, forgot password flows
• Deep links and push notifications handling
• Date/time & internationalization code
• Integration with Google Places API

• JavaScript
• HTML5
• CSS3
• Git
• GitHub
• NodeJS
• TravisCI
• Chrome DevTools
• IE DevTools
• PhantomJS
• GruntJS
• Fiddler
• bash

Core developer of an open-source UI framework & widget library, used by 100+ developers, and related tools.

• Shipped new features and bug fixes, with strong backward & cross-browser compatibility (down to IE7)
• Debugged compatibility issues in complex single-page web applications
• Improved test tools, CI / build automation reliability & performance
• Wrote docs and blog articles; technical support for external teams
• Internal technical expert role (1 of 5) in a team of ~15 developers
  • Contributed to technical discussions; established best practices
  • Code reviews, code integration; release management
  • Presented in several knowledge sharing sessions

Developed data warehouse middleware, full-text search engine; fixed bugs, wrote unit tests and builds.

• Java
• JSP
• SQL
• JUnit
• Struts
• Ant
• Lucene
• Eclipse

Implemented Single Sign-On & user profile area; email newsletter (backend, frontend, integration with SendGrid). Designed and implemented a mobile REST API.

• PHP
• MySQL
• CodeIgniter
• Doctrine ORM
• HTML
• CSS

Developed an IT system for the HR department (5-dev team).

• C#
• ASP.NET MVC
• HTML
• CSS

Implemented customer-facing websites and internal tools. Search-engine optimization.

• PHP
• Zend Framework
• MySQL
• HTML
• CSS
• SEO

Built and maintained websites for various customers, including local basketball team.

• PHP
• HTML
• CSS
• JavaScript
• MySQL
• SEO