Our application backend is primarily in Python/Django and we write most of our code in Python. We use a lot of other technologies like RabbitMQ, Celery, Tornado, Thrift, Memcached, etc. We also do a lot of interesting work in diverse areas, such as automated deployment, infrastructure, scaling, optimization, data mining, graph databases, Machine Learning, and we are always experimenting with new technologies.

You can checkout our engineering posts at http://engineering.hackerearth.com and developer APIs at http://developer.hackerearth.com.