Question 1

How do I store events when using Eventsourced in Elixir?

Accepted Answer

Eventsourced doesn't provide built-in event storage. You need to implement persistence yourself, such as using Ecto with a database or an event store like EventStore. The library focuses on the domain model, so you'll handle saving and loading events externally in your application layer.

Question 2

Eventsourced vs Commanded: which is better for event sourcing in Elixir?

Accepted Answer

Eventsourced is a lightweight library for functional event-sourced aggregates, ideal for teams wanting control over infrastructure. Commanded is a full CQRS/ES framework with built-in event bus, process managers, and persistence adapters. Choose Eventsourced for simplicity and customization; Commanded for out-of-the-box features and scalability.

Question 3

How to handle concurrency with Eventsourced aggregates?

Accepted Answer

Eventsourced doesn't handle concurrency directly. You need to manage it at the application level, such as using optimistic concurrency control by versioning aggregates when saving events to prevent conflicts, or implementing locking mechanisms in your event store.

Question 4

Best practices for testing Eventsourced domain models?

Accepted Answer

Leverage the simple testing approach shown in the README: invoke command functions and assert on pending events and resulting state. Use pattern matching to verify event structures and ensure business rules are enforced, making tests focused on domain logic without external dependencies.

Question 5

Can I use Eventsourced with Phoenix for web applications?

Accepted Answer

Yes, but integration is manual. Use Phoenix controllers to call command functions, persist events to a store, and update read models. Eventsourced handles the domain layer, so you'll need to bridge it with Phoenix for HTTP requests and real-time updates.

Question 6

How to implement snapshots with Eventsourced to improve performance?

Accepted Answer

Eventsourced doesn't support snapshots natively. You'd implement snapshotting yourself by periodically saving aggregate state and replaying only events after the snapshot when loading aggregates, which requires custom logic for state reconstruction and version management.

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