“I was amazed at how fast Quick Left was able to jump into the code and actually start contributing back. There’s always the fear that someone will have a hard time getting up to speed and that leads to a lot of downtime. Quick Left put that fear to ease with having code up for review on the very first working day.”

— David Cramer, Engineer @ Sentry



To provide momentum on the Backbone to React conversion of Sentry’s hosted app and author a front-end test suite infrastructure while Sentry hired more engineers to their in-house team.


Scoping & Services

Client provided a unique opportunity to work on an open source React project and apply React testing expertise. Quick Left provided Sentry with a Team Boost, supporting their open source team, for React programming and testing knowledge. Quick Left helped client increase velocity and boosted React expertise. React gives Sentry more dynamic real time streaming on the site; quicker, better supported updates; and easier general maintenance.

Solutions and Technologies:

  • Backbone.js
  • React.js
  • React testing
  • Flux, Reflux


Sentry builds infrastructure services that make the everyday lives of engineers easier. It does so by logging events within a code base, surfacing errors, helping to gauge severity and frequency, and giving valuable information to help companies fix those errors quickly.

Every month billions of exceptions are processed by Sentry infrastructure from the biggest names in Silicon Valley. Oh, and it's all open source. The hosted version of Sentry, that is,, is run by using the open source version of Sentry with a bit of proprietary code on top. That said, nearly every change that is needed for the hosted version to work is actually made upstream first, usually in the form of an extensible interface.

So, why bring in Quick Left? The main component of Sentry’s web app is the live feed, where customers can get to-the-minute information about the exceptions in code base. This was previously written in Backbone, but due to it’s superior UI, it was a good choice to switch the application to React.

Quick Left jumped on with Sentry’s engineering team to help increase velocity and provide previous expertise in React testing. The Quick Left engineers participated in the Sentry’s Agile processes and were added to the internal Slack channel; they began working seamlessly as members of the team.

Going through bugs (in React and Javascript), working through memory leaks, consulting on implementation of React and Flux, and writing front-end tests were major parts of the team’s day.

Quick Left engineers revealed that their major learnings on the project had to do with deepening their understanding of live feed UI, navigating the external code reviews of an open source project, and dealing with the pressure to find the coolest gifs for their pull requests!

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