1. A system, comprising: a database system comprising multiple database partitions configured to store data associated with one or more work items associated with processing requests made through a service interface; a plurality of host computers configured to perform work items requested through the service interface, wherein performing at least some of said work items includes initiating one or more commit operations on one or more of said database partitions, wherein at least some of the commit operations comprise updating a state of a transaction processed by the service; wherein one or more of the host computers are configured to generate, on a per-host, per-database partition basis, commit latency values for the database partitions, wherein a commit latency value for a particular database partition is dependent on the latency of one or more previous commit operations directed to that particular database partition; wherein a given one of the host computers is configured to: determine, for a particular work item to be initiated on a respective one of the database partitions, that the given host computer's commit latency value for the respective database partition exceeds a commit latency threshold; and in response to said determine, reduce a load of work items on the respective database partition, wherein to reduce the load of work items, the given one of the host computers is configured to: postpone the particular work item on the respective database partition; and perform the particular work item after the postponement.