1. CQRS
Command Query Responsibility Segregation
IPIJ Lighting Talks
Piotr Pelczar
me@athlan.pl

2. CQRS
• Greg Young
• different model to update information
• than the model you use to read information
• http://martinfowler.com/bliki/CQRS.html

3. CQRS
http://berb.github.io/diploma-thesis/community/091_archtrends.html

4. Operation
L1 cache reference
Branch mispredict
L2 cache reference
Mutex lock/unlock
Main memory reference
Latency
0.5 ns
5 ns
7 ns
25 ns
100 ns
Compress 1K bytes w/ cheap algorithm
3,000 ns
Send 2K bytes over 1 Gbps network
20,000 ns
Read 1 MB sequentially from memory
250,000 ns = 0.25ms
Round trip within same datacenter
500,000 ns
Disk seek
10,000,000 ns
Read 1 MB sequentially from disk
20,000,000 ns = 20ms (-80x)
Send packet CA->Netherlands->CA
150,000,000 ns

5. Queues, RabbitMQ
• Simple queue
• Work queues
(one consumer)
• Publish/Subscribe
(many consumers)

6. Sample architecture

7. CQRS
Q&A?
Piotr Pelczar
me@athlan.pl