McKellar was an early employee and engineering manager at Ksplice, which was acquired by Oracle in 2011. In 2012, she co-founded Zulip, a chat software company.[5] In 2014, the company was acquired by Dropbox.[6] She has spoken at several conferences about outreach efforts to increase the diversity of open-source communities.[7][8]
From 2012 to 2014, she was a director of the Python Software Foundation.[9] In 2013, McKellar won the O'Reilly Open Source Award for her contributions to Python.[10][11] In 2016, she won the Women in Open Source Community Award, awarded by Red Hat.[12] She is a contributor to Twisted, a networking framework for Python.[13] From 2014 to 2017, she was a Director of Engineering and the chief of staff to the VP of Engineering at Dropbox.[14]
McKellar was a senior technical advisor for 16 episodes of the HBO show Silicon Valley.[15]
^McKellar, Jessica (June 2010). Monitoring the health of an open source project : a case study (Thesis). M.I.T. Master of Engineering thesis. hdl:1721.1/61174.