About Foursquare

What is Foursquare?

Foursquare is a free app that helps you and your friends make the most of where you are. When you're out and about, use Foursquare to share and save the places you visit. And, when you're looking for inspiration for what to do next, we'll give you personalized recommendations and deals based on where you, your friends, and people with your tastes have been.

Whether you're setting off on a trip around the world, coordinating a night out with friends, or trying to pick out the best dish at your local restaurant, Foursquare is the perfect companion.

Foursquare by the numbers (last updated January, 2013)

• Community: Over 30 million people worldwide
• Over 3 billion check-ins, with millions more every day
• Businesses: Over a million using the Merchant Platform (more information at foursquare.com/business)
• Employees: Over 100 between headquarters in New York, an office in San Francisco, and a lovely outpost in London.

When was Foursquare founded?

Foursquare co-founders Dennis Crowley and Naveen Selvadurai met in 2007 while working in the same office space (at different companies) in New York City. Working from Dennis' kitchen table in New York's East Village, they began building the first version of Foursquare in fall 2008, and launched it at South by Southwest Interactive in Austin, Texas in March 2009.

Learn more by following Dennis' A brief history of Foursquare list!

Who are Foursquare's investors?

We're funded by Union Square Ventures, O'Reilly AlphaTech Ventures, Andreessen Horowitz, Spark Capital and a handful of angel investors.

How can my business, brand or agency work with Foursquare?

Whether you're a mom-and-pop shop, a national chain, or a brand, Foursquare can provide you with tools to engage with your customers and fans. Please visit foursquare.com/business for information on how you can start working with Foursquare.

I have a cool idea for a social service. Is there a way to build this onto Foursquare?

Yes! Just like Twitter, Foursquare has an API that allows developers to build their ideas on the Foursquare platform. Developers have already used the API to build new check-in functionality, cool games, and interesting data visualizations. You can read up on the documentation here.

Is Foursquare hiring?

Yes! We're always looking to hire amazing talent for our New York and San Francisco offices. For a list of open positions, check out foursquare.com/jobs.

So is it ‘check-in’ or ‘check in’?

It’s both! When you use it as a verb, it’s ‘check in.’ (For example, “Are you going to check in here? They have a free massage Special.”) ‘Check-in’ is the noun form. (For instance, “That was my most amazing check-in ever, I can't believe I got a free massage!”) And never use checkin. Every time you do, we cry on the inside.

I'm really into technology. What's Foursquare built on?

Because of our pretty insane growth, we’ve designed our entire software stack to be as flexible and scalable as possible. It’s allowed us to go from a few thousand users to tens of millions, and also to easily add more amazing engineers and get them contributing right away.

Foursquare is currently hosted within Amazon's EC2 service, using hundreds of servers running a bare bones version of CentOS Linux. We use NGINX to route requests and serve static content, and HAProxy to load balance web and API requests across many machines.

Then we get to the fun part. Moving up the stack, the live site data is stored in MongoDB (though we use Memcache to cache a small set of expensive calculations). For offline data analysis we regularly snapshot our live data and import it into a Hadoop cluster. We have some custom MapReduce jobs, but mostly rely on Hive's simple query syntax and a custom built job scheduler for regular calculations. We use Solr and Elasticsearch for powering venues, tips, users, and events search. Our search geo-indexing uses Google's s2 library to store cellids within our search index. We use PostGIS and the wonderful geonames.org dataset to reverse geocode addresses into coordinates, which allows us to place venues on a map and make them available for location-based search. Kestrel is our queue for asynchronous tasks that we wish to perform out of band of users' requests. User generated photos are stored on Amazon S3 with content delivery through Akamai. There is a bit more complexity if you dig deeper, but that’s the heart of it.

Almost all of the code for the web site, API, and batch processing is written in Scala. The web and API are built on top of the Lift web framework. We also use a good bit of Python and Bash scripting for automating build, deployment, and operations tasks. Finally, the dynamic content on the web site is written in javascript with a mix of jQuery, Backbone.js for object models, and Soy for templating.

We use beautiful maps by MapBox created using data provided by the wonderful © OpenStreetMap and contributors, and licensed Open Data Commons Open Database License. The interactive maps are generated using the open-source library Leaflet.

And we’re constantly pushing the limits and trying new things. Want to come join us? We’re looking for world-class engineers who want to do amazing things.

You can learn more about the technology we use on our engineering blog and on our github.