This document discusses Spotify's approach to optimizing ad yield on its platform. It describes how Spotify uses a subset of impression data, filters it by criteria like location and age, and extrapolates the results using a simple growth model to forecast available ad impressions at scale in real-time. Some challenges addressed include organic growth, cold starts for new markets, and seasonality. The solution uses Hadoop to store log data, Postgres for booked campaigns, and a forecasting engine to handle queries over filtered and extrapolated data.