Change Data Capture Event is the best option to meet this requirement. Change Data Capture Event is a type of streamingevent that notifies subscribers of changes to Salesforce records, such as creation, update, delete, and undelete operations1. By subscribing to Change Data Capture Event for the Case object, the dashboard component can receive real-time updates on the number of closed Cases. Push Topic Event is another type of streaming event that notifies subscribers of changes to Salesforce records that match a SOQL query2. However, Push Topic Event has some limitations, such as not supporting all SOQL features and not capturing delete and undelete operations3. Platform Event is a type of streaming event that delivers custom notifications within the Salesforce platform or from external sources4. Platform Event is not suitable for this requirement because it is not tied to Salesforce records and requires custom logic to publish and subscribe. Generic Event is a type of streaming event that sends custom JSON notifications to subscribers without a predefined schema5. Generic Event is not suitable for this requirement because it is not tied to Salesforce records and requires custom logic to publish and subscribe.