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CQRS

Command Query Responsibility Segregation separates write behavior from read behavior.

This page shows how ForgingBlocks concepts can be projected to support a CQRS-style design.

Important

ForgingBlocks does not require CQRS.
This page presents it as an architectural pattern, not a requirement.

Quick summary

Command Query Responsibility Segregation (CQRS) separates write behavior from read behavior. This page shows how ForgingBlocks concepts can be projected to support CQRS — not required.

Mapping:
- Commands — Express intent to change state (Command, CommandHandler, WriteOnlyRepository)
- Queries — Retrieve information (Query, QueryHandler, ReadOnlyRepository)
- Models may diverge over time (separate read/write stores with replication)

Fits when: read/write workloads differ significantly; scalability dominates; eventual consistency acceptable.

Conceptual mapping

  • Commands express intent to change state.
  • Queries retrieve information.
  • Read and write responsibilities are separated.
  • Models may diverge over time.

The diagram below shows a canonical CQRS view from the literature.

---
title: CQRS (Command Query Responsibility Segregation)
---
graph LR
    Client -->|send| CommandHandler[Command Handler]
    Client -->|fetch| QueryHandler[Query Handler]
    CommandHandler -->|save| WriteStore[Write Store<br/>RepositoryPort]
    QueryHandler -->|get_by_id/list_all| ReadStore[Read Store<br/>ReadOnlyRepository]
    WriteStore -.->|replicate| ReadStore

When this style fits

  • Read and write workloads differ significantly.
  • Scalability concerns dominate.
  • Eventual consistency is acceptable.