Tair is a distributed key-value data storage system originally developed at Taobao in 2008. It evolved from earlier key-value storage systems called tdbm and tbstore. Tair uses a client-server architecture with separate config servers to manage metadata and data server clusters to store data. Key features include namespaces to avoid key conflicts, versioning for concurrent updates, expiration of data, and interfaces for deleting individual items or entire clusters of data. The system routes requests to servers using a lookup table based on hash values of keys modulo a constant rather than the number of servers. Tair provides a simple API and is widely used for caching and storage in Alibaba's e-commerce platforms.