Exploring CQRS and Event Sourcing

This guide is focused on building highly scalable, highly available, and maintainable applications with the Command & Query Responsibility Segregation and the Event Sourcing architectural patterns. It presents a learning journey, not definitive guidance. It describes the experiences of a development team with no prior CQRS proficiency in building, deploying (to Windows Azure), and maintaining a sample real-world, complex, enterprise system to showcase various CQRS and ES concepts, challenges, and techniques.

The development team did not work in isolation; we actively sought input from industry experts and from a wide group of advisors to ensure that the guidance is both detailed and practical.

The CQRS pattern and event sourcing are not mere simplistic solutions to the problems associated with large-scale, distributed systems. By providing you with both a working application and written guidance, we expect you’ll be well prepared to embark on your own CQRS journey.

Table of Contents

Journey 1: Our Domain: Conference Management System
Journey 2: Decomposing the Domain
Journey 3: Orders and Registrations Bounded Context
Journey 4: Extending and Enhancing the Orders and Registrations Bounded Context
Journey 5: Preparing for the V1 Release
Journey 6: Versioning Our System
Journey 7: Adding Resilience and Optimizing Performance
Journey 8: Epilogue: Lessons Learned
Reference 1: CQRS in Context
Reference 2: Introducing the Command Query Responsibility Segregation Pattern
Reference 3: Introducing Event Sourcing
Reference 4: A CQRS and ES Deep Dive
Reference 5: Communicating Between Bounded Contexts
Reference 6: A Saga on Sagas
Reference 7: Technologies Used in the Reference Implementation