Event brokering is a role played by middleware in facilitating event-driven application architecture. The minimum capability required to play the role of event broker is pub-sub messaging. All middleware products, including MOMs and ESBs, supporting pub-sub can play the role of an event broker and can be referred to as basic 'event brokers' when so deployed. Middleware products that additionally offer special support for event-centric use cases (for example, a persistent event ledger for analysis and event sourcing, or programmable extensibility for custom filtering and analysis) are 'advanced' event brokers.
The market for ESP platforms consists of software subsystems that perform real-time computation on streaming event data. They execute calculations on unbounded input data continuously as it arrives, enabling immediate responses to current situations and/or storing results in files, object stores or other databases for later use. Examples of input data include clickstreams; copies of business transactions or database updates; social media posts; market data feeds; images; and sensor data from physical assets, such as mobile devices, machines and vehicles.