Event-Driven CQRS & Event Sourcing

Comparable to: Kafka, RabbitMQ, CQRS/Event Sourcing systems

Key Concepts

Use the concepts below when they fit the task. Not every CQRS system needs all of them.

• Write side: Commands validate input and publish domain events via pubsub
• Read side: Multiple projections subscribe to events independently, building query-optimized views in state
• Event log: Events are appended to state as an ordered log (event sourcing)
• PubSub handles fan-out — one event reaches all projections and downstream consumers
• HTTP triggers expose both command endpoints (POST) and query endpoints (GET)

Architecture

HTTP POST /inventory (command)
  → cmd::add-inventory-item → validate → append event to state