  Etsy is a global marketplace where people across the world connect to make,
buy and sell unique goods. Sellers at Etsy can promote their product listings
via advertising campaigns similar to traditional sponsored search ads.
Click-Through Rate (CTR) prediction is an integral part of online search
advertising systems where it is utilized as an input to auctions which
determine the final ranking of promoted listings to a particular user for each
query. In this paper, we provide a holistic view of Etsy's promoted listings'
CTR prediction system and propose an ensemble learning approach which is based
on historical or behavioral signals for older listings as well as content-based
features for new listings. We obtain representations from texts and images by
utilizing state-of-the-art deep learning techniques and employ multimodal
learning to combine these different signals. We compare the system to
non-trivial baselines on a large-scale real world dataset from Etsy,
demonstrating the effectiveness of the model and strong correlations between
offline experiments and online performance. The paper is also the first
technical overview to this kind of product in e-commerce context.
