Until recently, when our customers created a campaign, they could choose to target the whole world, the U.S. or create a list of specific countries and U.S. metros (e.g. the San Francisco Bay Area, the Atlanta metro, etc.). Last week, we added the ability to target *or* exclude countries, metros, regions (e.g. states in the U.S., provinces in Canada,…), cities and postal codes. That meant doing a significant refactor of our geolocation code, which lead me to (finally) use `Deferred` objects.
