1. A method comprising: receiving a first signal at a computing device comprising a processor, wherein the first signal includes information corresponding to a first user identifier associated with a first user; modifying a value of a first bit of a bitmap index responsive to the first signal, wherein the bitmap index includes a plurality of bit strings, wherein a value stored in a particular location in each of the bit strings indicates whether a corresponding signal associated with a corresponding user identifier has been received, and wherein the first bit is stored in a first location of the bitmap index that corresponds to the first user identifier and to the first signal; receiving a second signal that includes second information corresponding to a second user identifier associated with a second user; modifying a value of a second bit of the bitmap index responsive to the second signal, wherein the second bit is stored in a second location of the bitmap index that corresponds to the second user identifier and to the second signal; receiving a query directed to the bitmap index; and outputting a result of the query based on executing a query execution plan for the query, wherein executing the query execution plan comprises performing one or more set operations with respect to the first bit and the second bit.