What can be used in Salesforce to create a reactive integration with platform events?

The correct choice is CometD because it is a scalable HTTP-based event routing bus that allows for real-time integration with Salesforce platform events. CometD supports the Bayeux protocol, which enables clients to subscribe to a channel and receive updates whenever a platform event message is published. This makes it ideal for reactive integrations where applications need to react immediately to events.

Using CometD, developers can establish a connection to the Salesforce server, listen for events on specific channels, and then take action (like updating user interfaces or triggering other processes) in response to those events. This capability is pivotal in environments that require real-time data updates, such as dashboards or applications that need to reflect user interactions instantly.

Other options do not provide the same level of real-time event handling. The Generic API is more synchronous and designed for standard CRUD operations rather than real-time event handling. Apex special methods, while powerful for processing data and business logic within Salesforce, do not provide a mechanism for real-time subscription to events. Visualforce components are primarily for UI development and do not inherently handle event subscription or real-time data. Therefore, CometD stands out as the appropriate choice for creating reactive integrations with platform events in Salesforce.