When comparing Platform Events and Outbound Messaging for a near-real-time architecture, a Salesforce Platform Integration Architect must evaluate fundamental differences in their delivery models and governance. While both provide declarative, asynchronous "Fire-and-Forget" capabilities, their technical constraints differ significantly, particularly regarding scalability and platform limits.
The key architectural highlight in this scenario is that Platform Events operate on a specialized event bus with specific Event Publishing and Event Delivery limits. Unlike Outbound Messaging, which is governed by more general daily outbound call limits (often tied to user licenses), Platform Events have a dedicated allocation for the number of events that can be published per hour and delivered in a 24-hour period to external clients via the Pub/Sub API or CometD. For example, the number of concurrent subscribers to a Platform Event channel is typically capped at 2,000 for standard configurations. Since the customer expects 3,000 customers to view these messages, this limit is a critical evaluation point; the architecture would need to account for this gap, perhaps by using middleware to fan out messages to the larger audience.
In contrast, Outbound Messaging does not have an "Event Delivery" limit in the same sense. It is a point-to-point SOAP-based push mechanism where Salesforce manages retries for up to 24 hours if the receiving endpoint is unavailable. However, it is less flexible for multi-consumer scenarios because it requires a separate configuration for every unique destination.
Regarding the other options: Option A is incorrect because neither system strictly guarantees "exactly-once" delivery without the possibility of duplicates; in fact, Outbound Messaging may deliver a message more than once if it doesn't receive a timely acknowledgment. Option B is incorrect because Platform Events do not have built-in "fault recovery" handled by Salesforce in the same way as Outbound Messaging's automatic retry queue; with Platform Events, it is the subscriber’s responsibility to use a Replay ID to retrieve missed events within the 72-hour retention window. Therefore, highlighting the unique delivery and publishing limits is the most vital step for the architect.
