Overview

Notes on researching CQRS.

What is CQRS

• Command Query Responsibility Segregation
  • A pattern that separates responsibilities into Command and Query
    • Command
      • Performs data updates
      • Designed to focus on tasks rather than data
      • Expected to encapsulate the domain model of DDD
    • Query
      • Performs data retrieval
      • Designed as an object optimized for each use case
        • DTO
• Implementation Methods
  • Event Sourcing Pattern
    • In CQRS, events are commonly used to link commands and queries
  • www.ibm.com - Command Query Responsibility Segregation (CQRS) pattern
    • Discusses the gradual transition to CQRS
• Benefits
  • Can scale Read and Write independently
  • Can choose data sources for Read and Write separately
    • It is possible to keep the data source unified without separating
    • If separating data sources, data synchronization is required either synchronously or asynchronously
  • Simplifies the application-side model
• Drawbacks
  • Increases system components, leading to higher costs
  • Makes the overall network configuration more complex

Impressions

Deciding to implement this pattern feels quite challenging...

It seems there are many examples overseas, but I found that there are still few examples in Japan.

References

• microservices.io - Pattern: Command Query Responsibility Segregation (CQRS)
• learn.microsoft.com - CQRS Pattern
• learn.microsoft.com - Event Sourcing Pattern
• zenn.dev - Fully Understanding CQRS
• martinfowler.com - What Does "Event-Driven" Mean?
• martinfowler.com - CQRS
• docs.aws.amazon.com - CQRS Pattern
• logmi.jp - Chatwork's Tech Lead Discusses How to Use CQRS Effectively
• logmi.jp - "Doing CQRS" is Almost Synonymous with "Doing Event Sourcing": Design Philosophy Reflecting Reactive Systems and CQRS
• little-hands.hatenablog.com - Introduction to Practicing CQRS [Domain-Driven Design]
• hireoo.io - Creating a Microservice to Process Statistical Data Using the CQRS Pattern
• speakerdeck.com - Explaining CQRS/Event Sourcing in a Nutshell
• blog.j5ik2o.me - Why Does CQRS Become Event Sourcing?
• note.com - Can CQRS Be Achieved Without Event Sourcing?
• appmaster.io - Applying CQRS and Event Sourcing in Microservices
• www.ibm.com - Command Query Responsibility Segregation (CQRS) pattern
• www.eventstore.com - CQRS
• blog.risingstack.com - When Should You Use CQRS?
• logmi.jp - "Autonomy" Means Nothing if It Doesn't Function Independently: Considering the Advantages and Disadvantages of CQRS from Command and Query Requirements
• pages.awscloud.com - The Role and Implementation of CQRS & Event Sourcing in Modern Architecture