When building EDA applications, it’s important to know the different types of events you can publish, each has their own trade-offs.

Notification Events

• Minimal information
• Less risk of data being out of sync
• Consumers often need to fetch data
• Increases architecture coupling (callback for info)
• Producer/Consumer contracts kept minimum
• Lower risk of breaking contracts

Event-Carried State Transfer

• Enriched events (stateful)
• Higher risk of data being out of sync
• Consumers have the data
• Decreases architecture coupling
• Producer/consumer contracts more coupled
• Higher risks of breaking contracts

Delta events

• Stores difference between old/new
• Examples seen in change data capture events
• Can reduce complex in consumers needing to figure out what has changed

Domain Events

• Events that raised in the same bounded context
• Some folks reference these as internal events raised in bounded context
• Some folks reference these as business “important” events.
• People also refer to “integration” events. These are events used for integrations.

Extra Resources

• Best practices to design your events in event-driven applications - A talk I gave in 2022 around event design and trade-offs to consider.
• What do you mean by “Event Driven?” - Martin Fowler dives into event-driven architecture and talks about the different types of events
• The Event-Carried State Transfer Pattern - A great blog post on what ESCT is
• The event notification pattern - A great blog post on what notification events are