A practical walkthrough of building event-driven projections in Marten (a .NET event store on PostgreSQL). Covers three projection types using a helpdesk domain: SingleStreamProjection for incident details and short info, EventProjection for human-readable audit logs, and MultiStreamProjection for cross-stream customer dashboards. Also demonstrates custom event groupers to correlate data across streams without coupling projections, and explains when to use inline vs. asynchronous projection lifecycles.
