Abstract: A data storage service implements encoding techniques for generating compound partition keys, compound clustering keys, or a combination for more flexibility in storing data in a key-value database system. In some aspects a request to store data with multiple partition keys and/or multiple clustering keys may be received. Length information may be added to the partition keys, and the results concatenated together to form a compound partition key used to store the data in the database. Ordering information may be added to the clustering keys, and the results concatenated together to form a compound clustering key, to be used in storing and sorting data in the database. In some cases, the clustering keys may be made a uniform length, such as by padding keys, as necessary, to have a length that is a multiple of an arbitrary number, and then dividing the clustering keys into chunks of that arbitrary number.