1. A system for scheduling time intervals for a plurality of users comprising: database means, associated with one or more server means, for storing a profile for potential invitees of the system, the invitee profiles comprising user profiles wherein each user profile comprises information regarding available and unavailable times for that user; request generating means, connected over a network to the server means, for generating a request for allocation of a time interval for one or more of the plurality of invitees; busy time determination means for gathering the profiles for the one or more requested invitees using asynchronous fan out requests to the one or more databases storing the profiles, and for incrementally determining whether those invitees are available during the requested time interval as the profiles for each of said one or more requested invitees are gathered using said asynchronous fan out requests.