What Challenges of Event-Based Pattern

Guaranteed delivery. In some systems, especially in IoT scenarios, it's crucial to guarantee that events are delivered.

Processing events in order or exactly once. Each consumer type typically runs in multiple instances, for resiliency and scalability. This can create a challenge if the events must be processed in order (within a consumer type), or if the processing logic is not idempotent.

The amount of data to include in an event can be a significant consideration that affects both performance and cost. Putting all the relevant information needed for processing in the event itself can simplify the processing code and save additional lookups. Putting the minimal amount of information in an event, like just a couple of identifiers, will reduce transport time and cost, but requires the processing code to look up any additional information it needs.