projection-patterns

To build read models from event streams, you process events through projectors that apply state changes to data stores like SQL databases or Elasticsearch. This requires defining event handlers and managing projection checkpoints for stateful processing.

Implementing CQRS read sides and materialized views involves creating projectors that consume event streams to populate denormalized data stores. This enables faster querying by maintaining separate read-optimized representations of event data.

Populating Elasticsearch with event data for real-time dashboards is done by processing events through projectors that apply updates directly to search indexes. This allows live data visualization by maintaining queryable projections from continuous event streams.

Yes, managing projection checkpoints is required for stateful event processing. Checkpoints track the position of consumed events, ensuring reliable recovery and consistent state synchronization between the event stream and read models.

Yes, asyncpg can be used to maintain SQL projections from event streams. The system supports applying projected events to SQL databases, allowing you to update tables like order summaries automatically when new events occur.

You should avoid using projections when your system does not require complex read models, real-time dashboards, or search indexing. Projections add architectural overhead through checkpoint management and event handler maintenance, making them unnecessary for simple CRUD applications.