Disclosed are various embodiments for prioritizing service requests. A load associated with a service is determined. A request destined for processing by the service is received. One or more client-specified parameters are determined from the request. The client-specified parameters include one or more of: a droppability parameter indicating whether the request is droppable, or a deadline parameter indicating a deadline for completion of processing of the request. When the load meets a threshold, a prioritization is assigned to the request based at least in part on the client-specified parameter.