A computer-implemented method of adjusting usage of shared computing resources, comprising: under control of one or more computer systems configured with executable instructions, receiving a request for an adjusted committed request rate for a customer with respect to a type of resource, the customer having a current committed request rate for the type of resource, the request capable of specifying a committed request rate corresponding to any portion of a capacity of one or more instances of the type of resource, wherein the committed request rate for a type of resource is a committed rate of input/output operations per second, IOPS, for a data server; if the adjusted committed request rate is less than the current committed request rate, automatically reducing the committed request rate for at least one instance of the type of resource for the customer; if the request relates to increasing the committed request rate, automatically committing (710, 712) at least a portion of an available committable rate capacity of at least one instance of the type of resource to obtain the adjusted committed request rate; and storing information for the adjusted committed request rate for the customer for use in managing a rate of request handling for the customer; wherein the adjusted committed request rate is capable of being supplied by a single determined instance or a plurality of determined instances each providing at least a portion of the requested committed request rate, each determined instance further capable of having additional customers sharing the resource when request capacity for the instance allows for the additional customers. under control of one or more computer systems configured with executable instructions, receiving a request for an adjusted committed request rate for a customer with respect to a type of resource, the customer having a current committed request rate for the type of resource, the request capable of specifying a committed request rate corresponding to any portion of a capacity of one or more instances of the type of resource, wherein the committed request rate for a type of resource is a committed rate of input/output operations per second, IOPS, for a data server; if the adjusted committed request rate is less than the current committed request rate, automatically reducing the committed request rate for at least one instance of the type of resource for the customer; if the request relates to increasing the committed request rate, automatically committing (710, 712) at least a portion of an available committable rate capacity of at least one instance of the type of resource to obtain the adjusted committed request rate; and storing information for the adjusted committed request rate for the customer for use in managing a rate of request handling for the customer; wherein the adjusted committed request rate is capable of being supplied by a single determined instance or a plurality of determined instances each providing at least a portion of the requested committed request rate, each determined instance further capable of having additional customers sharing the resource when request capacity for the instance allows for the additional customers.