Dynamic data partitioning for stateless request routing

Dynamic data partitioning for stateless request routing may be implemented. Respective partitions of data and corresponding mapping information may be maintained at partition hosts. A repartitioning event may be detected for the data to move a portion of data from a source partition host to a destination partition host. In response, the mapping information at the source partition host may be updated to indicate that the portion of data is located at the destination partition host for subsequent access requests received at the source partition host. The portion of the data may be copied from the source partition host to the destination partition host. Upon completion of the copy of the portion of the data, the mapping information at the destination partition host may be updated to indicate that the portion of the data is located at the destination partition host and is available for access.