Mountain View, CA (we also love interns, and remote is a possibility for the right candidate)

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At Khan Academy, we're a small, 52-person non-profit tech startup. We're trying hard to do good for the world. Here's a testimonial we received just two days ago:

January 29, 2014

I am an adult returning to school for a midlife career change. I have always disliked math and thought I was bad at it -- and my last math class was over 20 years ago! But I just passed my Accuplacer placement test, thanks to Khan Academy. Thank you so much for making it fun and easy to refresh my skills. I also purchased the Accuplacer test prep app, but I found myself coming back to Khan Academy more often because I liked it more. Now I am learning coding at school, so I'll definitely be back for more!

Lisa

This letter is one story, but every month we hear about hundreds of lives like this that we've transformed.

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Most of you reading this are familiar with Sal's videos, but we also have hundreds of videos by other teachers, partnerships with organizations like MoMA and the California Academy of Sciences, and a huge library of interactive exercises. Over 20 million math problems are done every week on our site. That's a lot.

With this huge scale, we're able to study learning in a way that wasn't previously possible. We've run tests and found that students learn more when they're given harder problems based on an intelligent machine-learning algorithm [1]. Right now we have dozens of A/B tests running to help us understand what we can do to make people learn more, such as testing how different spaced repetition algorithms affect retention. We're also beginning to release anonymized student data to external researchers.

We're doing a big mobile push. Around 20% of our traffic comes from phones and tablets but we have only two mobile devs so far. We're totally overhauling our iOS app; if you join us now, you can be a main developer on an app that is guaranteed to have millions of users. This is a rare opportunity.

You'll be working alongside a small team with the best in the business â€“ though we have "celebrity" devs like jQuery creator John Resig and Google's first employee (and former Director of Technology) Craig Silverstein, we have many more you haven't heard of but who are also amazing.

Whether you're a machine learning guru or you take pride in perfecting UI details for a dropdown menu [2], we have something for you. We really have a great team and culture. We use (and contribute to) new technology [3], we invest heavily in mentoring our interns (and full-timers) [4], we have lots of fun at and around work [5], and even though we're a non-profit, we pay well too. I'm also proud to say that we're winning against GitHub in team Bensity (i.e., percentage of employees named Ben) [6].

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We're hiring engineers (frontend, backend, mobile, data science), designers, and more -- if you're a designer, you might also be interested in our parnership with Bridge [7]. And if you want to have an amazing summer (or fall or spring) building real features for real users, we're hiring interns too.

As I said above, mobile is a big priority for us. Let me know if you know someone great.

Please apply at https://www.khanacademy.org/careers directly (say you saw us on HN!). If you have questions, feel free to ask here or to email me at alpert+HN@khanacademy.org.

[1]: http://derandomized.com/post/51729670543/khan-academy-machin...

[2]: http://bjk5.com/post/44698559168/breaking-down-amazons-mega-...

[3]: http://joelburget.com/backbone-to-react/ (sorry about the background, but there are dinosaur pictures!)

[4]: http://bjk5.com/post/71559049069/the-most-common-feedback-we...

[5]: http://life.khanacademy.org/

[6]: https://twitter.com/dmnd_/status/425870378330644480

[7]: http://www.khanacademy.org/about/blog/post/75079597750/khan-...