Based on the values of selected fields in incoming events, the correlator segregates events into many separate partitions. Partitions typically relate to real-world entities that you are monitoring such as bank accounts, cell phones, or subscriptions. For example, you can specify a query that partitions Withdrawal events based on their account number. Each partition could contain the Withdrawal events for one account. Typically, a query application operates on a huge number of partitions with a relatively small number of events in each partition.

Each partition is identified by a unique key value. You specify a key definition in each input definition in the query's inputs block. The key definition specifies one or more fields in the event type you want to monitor. The number, order and type of the key fields must be the same in each input definition in a query.

A query operates on the events in the windows in each partition independently of the other partitions.