Exam Plat-Arch-204 Topic 3 Question 26 Discussion

In a robust event-driven architecture, "durability" is the ability of a system to retain events so that a subscriber can retrieve them even after being offline. For an architect needing to minimize data loss over "every couple of days," the selection must focus on event types that support a high retention window.
Salesforce provides two modern event types specifically designed for high-scale, durable messaging:
Change Data Capture (CDC): This automatically broadcasts changes to Salesforce records (Create, Update, Delete, Undelete). CDC events are highly durable and are retained in the event bus for 72 hours (3 days).
High-Volume Platform Events: These are custom events defined by the architect. Like CDC, High-Volume Platform Events also provide a 72-hour retention window.
Earlier versions of the Streaming API, such as PushTopic Events and Generic Events (Option C and parts of A), typically offered a 24-hour retention window, which would not satisfy the requirement of a client re-connecting "every couple of days" (potentially 48-72 hours later).
By utilizing CDC and High-Volume Platform Events, the architect can leverage the Replay ID. When the client re-connects, it can send the Replay ID of the last event it successfully processed. Salesforce then "replays" all events that occurred during the client's downtime from that specific point, up to the 72-hour limit. This mechanism ensures zero data loss for planned or unplanned outages lasting up to three days, making it the most resilient choice for the specified requirements.