1. A method for identifying a particular database shard associated with a given user, the method comprising: receiving a data request associated with a first user; determining a shard level assigned to the first user, the shard level corresponding to a set of database shards that were active within a data management system when data associated with the first user is first stored in the data management system; selecting a shard function corresponding the shard level from a set of shard functions, each shard function in the set of shard functions corresponding to a different shard level; and inputting a user identifier associated with the first user into the shard function to identify a first database shard in the set of database shards that stores data associated with the first user; and processing the data request using the first database shard.