A collection of literature I recommend for reading on Event Sourcing/Event Stores and CQRS, to be extended over time. Ranges from high-level beginner material to implementation details and code samples.

Event Sourcing

• Event Sourcing: Entry in Martin Fowler’s bliki
• Event Sourcing Basics: Introduction to Event Sourcing in the documentation of (Get)EventStore
• Aggregates and Event Sourcing: A+ES: Appendix A contributed by Rinat Abdullin in Vaughn Vernon’s IDDD book (see below).
• Introducing Event Sourcing: A chapter in the CQRS Journey e-book
• Event Sourcing in a CQRS wiki
• Events as a Storage Mechanism by Greg Young
• Event Sourcing a la Lokad by Rinat Abdullin
• Event Sourcing as a strategic advantage by Jimmy Bogard
• A better domain events pattern by Jimmy Bogard
• Aggregates and their events by Yves Reynhout
• Value objects in an event sourced domain model by Yves Reynhout
• Event Sourcing Revisited, Event Sourcing applied - the Aggregate, Event Sourcing applied – the application service, Event Sourcing applied – the Repository blog post series by Gabriel Schenker

Code

• NEventStore CommonDomain: Originally by Jonathan Oliver and now maintained as part of the NEventStore project, the CommonDomain is a great foundation for C# applications that want to use Event Sourcing and can also serve as a reference for ports into other languages.
• IDDD Sample application: The “Collaboration” Bounded Context of Vaughn Vernon’s sample code for this IDDD book (see below) uses event sourcing, see, e.g., the Discussion AR derived from the EventSourcedRootEntity. This sample can get you started with Event Sourcing in Java very quickly.
• Lokad IDDD Sample: the source code for Rinat Abdullin’s chapter in the IDDD book (C#)
• .NET Event Sourcing: a lightweight framework for .NET, attempts to fill in the gaps between NServiceBus and NEventStore.
• AggregateSource: A lightweight infrastructure for doing eventsourcing using aggregates in C# by Yves Reynhout; see also AggregateSource Testing

Testing

• Scenario-based Unit Tests for DDD with Event Sourcing
• Axon framework - behavior driven testing - we are not using Axon, but the BDD Given–When–Then pattern presented is quite powerful
• Trench Talk: Assert.That(We.Understand()); by Yves Reynhout on BDD testing with ES

Event Store

• Building an Event Storage by Greg Young
• Your Coffee Shop Doesn’t Use Two-Phase Commit by Gregor Hope
• How I Avoid Two-Phase Commit and Removing 2PC (Two Phase Commit): Jonathan Oliver on how NEventStore avoids expensive 2PCs
• Your EventStream is a linked list by Yves Reynhout

Code

• NEventStore: The implementation of the popular event store for .NET is a must-read: It’s very well designed and the code is easy to understand. It can serve as a template for implementation in other languages — in fact, our own JEEventStore was heavily influenced by it.

CQRS (including CQRS+ES)

• DDDCQRS mailing list: Worth reading the archive.
• CQRS: Entry in Martin Fowler’s bliki
• Eventually Consistent - Revisited article by Werner Vogel, CTO of Amazon
• CQRS Journey long e-book on CQRS by a Microsoft team, a must-read
• Command-Query Responsibility Segregation: video/slides of a talk by Udi Dahan at QCon
• CQRS Starter Kit and FAQ
• Clarified CQRS by Udi Dahan
• Busting some CQRS myths by Jimmy Bogard — definitely worth reading ]
• Why you should be using CQRS almost everywhere… by Udi Dahan
• When to avoid CQRS by Udi Dahan
• CQRS and Event Sourcing by Greg Young
• Why I Still Love CQRS (and Messaging and Event Sourcing) by Jonathan Oliver on benefits of CQRS+ES, many links included

• CQRS: Out of Sequence Messages and Read Models by Jonathan Oliver

• CQRS and user experience by Jimmy Bogard
• CQRS – Use Your Common Sense by Steve Bate
• CQRS Event Sourcing: Validate UserName uniqueness: Stackoverflow question on a very common use-case: uniqueness constraints
• Eventual Consistency and Set Validation: Greg Young on uniqueness constraints
• Secondary indexes and constraints on the write side: Yves Reynhout on uniqueness constraints

Code Samples

• Greg Young’s SimpleCQRS example: small C# sample project that let’s one quickly grasp the CQRS principle
• Lokad.CQRS Sample Project An advanced (and complex) CQRS sample project
• CQRS Journey Code: the CQRS Journey sample application for the e-book
• SimpleCQRS by Tyrone Groves (C#)

DDD

• Domain Driven Design: The blue book by Eric J. Evans
• Implementing Domain Driven Design: A book by Vaughn Vernon, which I can recommend even more than Evan’s original book; if you want to read only one book on the topic, read this.
• Don’t Create Aggregate Roots by Udi Dahan
• FAQ on Aggregates
• FAQ on Sagas

Messaging

• The LMAX disruptor: Entry in Martin Fowler’s bliki. The LMAX disruptor a high-performance, single-threaded messaging architecture for the JVM that for a financial application handles up to 6 million order per second. Even if such scalability is way out of scope of most projects, you should be aware of it.
• NServiceBus: The most popular service bus for .NET. If you are going to use CQRS+ES in a C# project, you should look at this.

Updates to this post

• 2015-07-15: Added Gabriel Schenker’s blog series on Event Sourcing.

Related Posts

• 15 Jul 2015 » JEEventStore - Design Rationale and Feature Wishlist
• 02 Sep 2014 » Building an Event Store for Java