CQRS/ES AND FRIENDS Possibly distributed systems... intentionally

WHY DO WE NEED YET ANOTHER SHINY?

Is this an Architecture? No: a bunch of patterns

Sorry I don’t cook

Less how should it be, more what should it do

WHY DDD IS RELEVANT

Ubiquitous language

Bounded contexts

Aggregates

If you are looking for intention, there is a way to

persist it

Legacy systems anyone?

IF

I WA

S T

RY

ING

TO

LE

AR

N C

QR

S N

OW

CQRS/ES

CQRS: “Separate command messages that

change state from query messages that read

state.”

Event Sourcing: Capture changes to an

application state as a sequence of events.

AND FRIENDS

Eventual Consistency

Messaging

QUERY

Query Side: asking a question should not change

the answer.

TASK BASED UIS

COMMAND

Tell the system what to do

Has a well defined intention

EVENT

Occurrence

If using messaging, possibility of integration.

CONSEQUENCE

Compensating actions -> there is no big eraser

here

Automatic audit log

Since there are no queries to read… the

aggregate roots have fewer relationship and their

boundaries are better defined

AN EXAMPLE

1. Add Item to cart

2. The product is not in stock

THANKS

Andrea Magnorsky

@silverspoon

www.roundcrisis.com

I wantz sleeps, its

Caturday