dynamic-consistency-boundary

You can achieve multi-stream consistency without sagas by implementing the Dynamic Consistency Boundary pattern, which handles command invariants spanning multiple event streams selected by query using Wolverine and Marten. This approach avoids saga coordination entirely.

A dynamic consistency boundary is a pattern for maintaining consistency across multiple event streams. In .NET, it uses Wolverine and Marten to select events by tags via EventTagQuery, allowing commands to enforce invariants that span streams without saga coordination.

Tag-type registration for EventTagQuery in Marten requires using a .NET-10 Guid-wrapper for the tag types. This setup allows the Dynamic Consistency Boundary pattern to correctly select and aggregate events across multiple streams based on those tags.

When applying a dynamic consistency boundary, you must handle the DcbConcurrencyException to manage concurrent write conflicts. This exception occurs during multi-stream event processing and ensures tag-based invariants remain consistent during parallel command execution.

Yes, Wolverine and Marten are required dependencies to implement the dynamic consistency boundary pattern. They provide the underlying event sourcing infrastructure and command handling necessary to execute multi-stream tag queries and boundary models.

Use a dynamic consistency boundary instead of a saga when a command's invariants span multiple event streams that can be selected by query. This pattern provides an alternative to saga coordination by fetching events for writing using tags and a boundary model.