Event-driven applications perform based on events, which are things that take place in the application and trigger a response. Event-driven applications are designed with event-driven programming, a programming paradigm in which events that occur trigger a series of actions. These actions are programmed into the application so that they’ll always happen when a corresponding event takes place. Events contain metadata, additional details about the event.
Examples of event-driven applications
Event-driven applications feature real-time responses and are often a better solution for businesses that require instant actions or notifications. To show how event-driven apps can work, here are a few examples:
- Home security applications might notify a homeowner when someone comes to their front door. An event might occur when the nearby sensor or camera picks up motion from the door. That event triggers a response that eventually results in informing the homeowner that someone is at their door.
- On the social app GroupMe, actual, physical events (not “events” as we use the term here) that a user creates, such as a birthday party, triggers reminders to the app. Reminders like “Birthday Party is starting in one day” or “Birthday party starts in one hour” don’t come from humans managing the app; they happen automatically because the event triggers those notifications.
- In banking, an app might be programmed to flag large transactions or something that appears fraudulent. When a large transaction or fraudulent activity occurs, that event triggers a response, like a notification to the account owner.
Event-driven apps are part of event-driven architecture, an entire application infrastructure based around responding to events. This architecture, known as EDA, better meets the demand for real-time response to data than previous systems. Previous technology required human users to make a request from a system and then wait for a response. In development, it’s sometimes known as request-driven programming. This is a slow process compared to event-driven applications.
How do event-driven applications work?
Event-driven applications are programmed to react in a certain way to an event. This triggered response, known as an event loop in programming, can’t be altered once it has begun. Event-driven apps are more complex to design and program than other applications (like a request-driven one) because they are more loosely coupled. However, that loose coupling means that all the hardware and software involved don’t have to be completely connected, so event-driven apps are also more flexible. They don’t have to be constantly managed or told what to do.
Event-driven apps work by using an event broker. Event brokers might be a software platform or Software-as-a-Service and are responsible for transporting events to the correct location after receiving all event messages. Having a middle-man keeps the entire application from going down if one component fails.
Event-driven apps are typically hosted through serverless computing, based in the cloud. Serverless computing is better for handling large amounts of workloads and events. It enables on-demand application processes but doesn’t require constant server management.
Event-driven apps require real-time responses for uses such as delivery apps, business software, and web analytics tools.