The following figure shows the important characteristics of Reactive Systems:

The important characteristics are as follows:

• Responsive: Systems respond in a timely manner to their users. Clear response time requirements are set, and the system meets them in all situations.
• Resilient: Distributed systems are built using multiple components. Failures can occur in any of these components. Reactive Systems should be designed to contain failures within a localized space, for example, within each component. This prevents the entire system from going down in cases of local failure.
• Elastic: Reactive Systems stay responsive under varying loads. When under heavy load, these systems can add additional resources while releasing them when the load goes down. Elasticity is achieved using commodity hardware and software.
• Message driven: Reactive Systems are driven by messages (or events). This ensures low coupling between components. This guarantees that the different components of the system can be scaled independently. Using non-blocking communication ensures that threads are alive for a shorter period of time.

Reactive Systems are responsive to different kinds of stimulus. A few examples are as follows:

• React to events: Built based on message passing, Reactive Systems respond quickly to events.
• React to load: Reactive Systems stay responsive under varying loads. They use more resources under high loads and release them under lesser loads.
• React to failures: Reactive Systems can handle failures gracefully. Components of Reactive Systems are built to localize failures. External components are used to monitor the availability of components and have the capability to replicate components when needed.
• React to users: Reactive Systems are responsive to users. They do not waste time performing additional processing when consumers are not subscribed to specific events.