In other cases, open source technologies deployed in the cloud by Zillow have won out. Zillow started with Microsoft SQL Server as its primary data store, but on AWS it’s in the process of moving to Redis, an open source, key-value-pair database. Thind says the company considered migrating to AWS-native database service DynamoDB instead, but it was “just not cost-effective.” Zillow has also become a major Spark shop. According to Thind: Zestimate is composed of lots of different types of machine learning models, and we can run a lot of these models in parallel.