My (minimal) slides from the presentation I gave a

1. Let’s Learn Together Intro to CQRS Ted M. Young @jitterted Developer & Agile Coach Guidewire Software, San Mateo, CA Silicon Valley Code Camp – October 9, 2011 Creative Commons Attribution-ShareAlike (CC BY-SA 3.0)

2. What’s the Problem CAP Consistency Availability Partitionability

3. Can’t Have All Three CAP: Choose Two Consistency + Availability Sacrifice Partitionability E.g., single database, clustered database Consistency + Partitionability Sacrifice Availability E.g., pessimistic locking, distributed locking Availability + Partitionability Sacrifice Consistency E.g., optimistic locking, merging, expirations Many systems are like this: eventually consistent Whether you like it or not

4. BASE vs. ACID Basically Available Soft-state Eventual consistency Stale data is OK

5. What’s so bad about Eventual Consistency

6. BASE is Not New Inktomi Presentation in 1998

7. Not an either-or, but a spectrum BASE vs. ACID

8. CQRS Leans to BASE

9. CQRS is Command Query Responsibility Segregation

11. http://www.udidahan.com/2009/12/09/clarified-cqrs/

12. Command Mutator

13. Re-think UI No more CRUD? Stop The Forms

14. Query With respect to the queried data Read-Only

15. Resources: CAP, Other Background Bertrand Meyer Command-Query Separation, §23.1 (p. 751) Object-Oriented Software Construction, 2nd Ed. (ISBN 0136291554) Dr. Eric Brewer, Inktomi Presentation (1998) http://www09.sigmod.org/disc/disc99/disc/nsf_acad_ind/brewer/sld019.htm Dan Pritchett BASE and latency http://www.infoq.com/articles/pritchett-latency Prevayler http://prevayler.org/old_wiki/Welcome.html

16. Resources: CQRS-Specific Greg Young (no relation) CQRS and CAP http://codebetter.com/gregyoung/2010/02/20/cqrs-and-cap-theorem/ UdiDahan Good overview http://www.udidahan.com/2009/12/09/clarified-cqrs/ Martin Fowler’s CQRS http://martinfowler.com/bliki/CQRS.html Axon Framework (Java) http://www.axonframework.org

17. Resources: CQRS-Specific RinatAbdullin CQRS Starting Page http://abdullin.com/cqrs/ More useful info from Rinat with good PDF diagram http://abdullin.com/xlim/ PålFossmo Another nice blog entry on CQRS http://blog.fossmo.net/post/Command-and-Query-Responsibility-Segregation-%28CQRS%29.aspx

18. Thanks! Follow me on Twitter: @jitterted Email me: tyoung@guidewire.com [Guidewire is hiring devs and testers!] Final Questions?