Jonathan Klein, Developer in Boston, MA, United States
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Jonathan Klein

Verified Expert  in Engineering

Software Developer

Boston, MA, United States
Toptal Member Since
May 22, 2015

Jonathan is a Lead Engineer at, where he focuses on solving both front-end and back-end issues. He started the Boston Web Performance Meetup Group, and he contributes to a few open source projects, including the HTTPArchive, WebPagetest, and CSSLint. He is also the co-creator of Hound and wpt-script, two open source projects built at Etsy.

AngularJS, Apache, Ruby on Rails (RoR)
MySQL, React, JavaScript, Git, Chef, PHP
SQL, JavaScript, CSS, ASP, Subversion (SVN), PHP




Preferred Environment

Sublime Text 3, Vagrant, GitHub

The most amazing...

...tool I've open sourced is Hound, a code search tool built at Etsy.

Work Experience

Lead Engineer

2015 - PRESENT
  • Focused on front-end architecture and building a strong engineering team.
Technologies: AngularJS, Apache, Ruby on Rails (RoR)

Senior Software Engineer

2012 - 2015
  • Wrote public-facing site performance reports on Etsy’s “Code as Craft” blog, communicating quarterly load time metrics for
  • Deployed and managed a custom WebPagetest instance on Amazon EC2 cloud servers, which was used to monitor site performance.
  • Open-sourced wpt-script, a WebPagetest client that makes it easy to automatically run tests and gather data from WebPagetest.
  • Open-sourced Hound, a code search tool which became Etsy’s third most popular open source project within one month of launch.
  • Conducted performance audits across and built tooling to make regressions easier to identify and fix.
Technologies: MySQL, React, JavaScript, Git, Chef, PHP

Senior Software Engineer

2008 - 2012
  • Received 2009 “Founder’s Award for Innovation,” given to one employee each year hand-picked by the company founders out of 500+ candidates for outstanding contributions to the business.
  • Promoted three times in less than four years, which was dramatically faster than peers.
  • Led a team of five internal engineers and four remote contractors to rewrite's code base using PHP, incorporating site design and brand overhaul.
  • Trained and led a four-person CSS team during a redesign of all 200+ CSN Stores websites in 2009, establishing company-wide coding conventions and best practices.
  • Built new features for the customer-facing websites as well as back-end tools to make it easier for our marketing team to make data changes.
Technologies: SQL, JavaScript, CSS, ASP, Subversion (SVN), PHP

A code search tool that I built with another engineer during my time at Etsy.


PHP, HTML, CSS, JavaScript, SQL, Python


Ruby on Rails (RoR), Laravel, ASP, AngularJS


Memcached, PostgreSQL, MySQL


Front-end Development, Software Development


Node.js, jQuery, React


Subversion (SVN), Sublime Text 3, Packer, Vagrant, Chef, Git, Apache, GitHub


Agile Software Development


Amazon EC2

2004 - 2008

Bachelor of Science Degree in Astronomy and Physics

Haverford College - Haverford, PA