At Smartly.io we build tools for largest European eCommerce-sites and Ad Agencies to automate and optimize their Facebook advertising. We're about 18 months old, currently 24 (8 devs) people strong and growing fast. We have actual paying customers (see our frontpage), have raised funding from top investors in Finland like Lifeline Ventures (e.g. Supercell) and our team is a bunch of experienced startup veterans (founders of Startup Sauna, worked previously in SF etc.).
We're looking for full stack developers. There's plenty of interesting challenges to tackle, ranging from designing and building UI to handling large amounts of data and designing models for automatically optimizing bid levels.