1. A computer-implemented method comprising: receiving a request to perform an operation on a mapped object, wherein mapping data defines a mapping between said mapped object and a base object, said base object associated with content data; wherein said mapped object and said base object reside in a volatile memory cache; wherein the mapping data includes an indication of a first mapping type of a plurality of mapping types; wherein the mapping is only retained as long as said mapped object resides in said cache; responding to said request by examining the mapping data to determine that the mapping type of the first mapping is said first mapping type; and to complete the requested operation, performing a first sequence of one or more actions based on determining that the mapping type of the first mapping is said first mapping type; wherein the method is performed by one or more computing devices.