San Francisco / Portland, OR
Urban Airship has tons of engineering and other positions open: <a href="http://urbanairship.com/careers/" >http://urbanairship.com/careers/</a>
We help mobile app owners manage their users.  Customers drop our SDK into their app (iOS, Android, Windows, etc.), then they can go to our elegant web interface to send push notifications, setup triggered events, segment their audience, create a pass/offer for Passbook, and more.
There are over 1 billion app installs with our SDK in it.  Many customers are huge brand name apps you would recognize (10M+ users each).  That's a lot of devices we push data to, and it's a lot of data coming back when devices phone home (analytics data, location data, etc.).  Our engineering targets for push are 100,000 messages sent per second or more.  It's interesting because a lot of our traffic is outbound (us sending things to phones) as well as inbound (phones calling back to us).  It's kind of crazy, we have to make sure we don't DDOS ourselves and our customers.
I work on Audience Segmentation.  Customers can slice and dice who they want to send to.  We do a lot of GIS/location indexing, as well as indexing based on the preferences and behavior of mobile users.
Our engineering roles are available in Portland or San Francisco, your choice.  We also have a Digital Wallet team in Palo Alto that is going hard at Passbook and other digital wallet tools.
If you interested email me at ben (at) urbanairship (dot) com.  It's fun!
-Ben
Back-end Stack: Java (modular/modern), Protocol Buffers, Kafka, HBase, Hadoop (Mapr), some Cassandra. Front-end Stack: Python (Django), modern CSS/HTML, JavaScript, cool map interfaces