How do external applications publish events to Salesforce?

The correct answer highlights that external applications can publish events to Salesforce using the sObject API. This API allows external systems to interact directly with Salesforce objects, enabling them to create, update, and delete Salesforce records in real-time. The sObject API is specifically designed for working with Salesforce's data model and provides a straightforward mechanism for integrating external applications with Salesforce, including the capability to publish events that correspond to changes in the application’s data.

Utilizing this API, an external application can invoke the necessary operations that result in events being triggered within Salesforce, facilitating seamless connectivity and data synchronization. This makes it optimal for scenarios where immediate feedback or data interaction is needed.

While other APIs like the REST API are generally used for various CRUD (Create, Read, Update, Delete) operations and data manipulation, the sObject API is specifically tailored for handling Salesforce objects, which are central to event publishing in this context. Batch Apex and Bulk API serve different purposes focused on handling large volumes of data or executing asynchronous processes, but they are not primarily used for real-time event publishing from external applications.