1. Apparatus, comprising: a processor; computer memory holding computer program instructions that when executed by the processor improve an operation of a multi-tenant shared computing infrastructure by preventing or mitigating application-level denial-of-service with respect to compute resources in the multi-tenant shared computing infrastructure, wherein a set of tenant applications available in the multi-tenant shared computing infrastructure are accessible by one or more accessors that are permitted access, the computer program instructions comprising: program code to provide a set of accessor usage profiles, at least one accessor usage profile representing legitimate behavior in the multi-tenant shared computing infrastructure by defining a time period, at least one usage constraint, and an accessor type; program code operative upon receipt from an accessor of a request to access a given application in the multi-tenant shared computing infrastructure to select a given accessor usage profile from the set of usage profiles; program code operative upon matching the accessor type to apply the at least usage constraint in the selected accessor usage profile with respect to the defined time period to determine whether the request to access the given application should proceed; and program code responsive to a determination that permitting the request to access triggers the at least one usage constraint in the selected accessor usage profile with respect to the defined time period, to provide the given application a notification.