1. Beyond DDD: uno sguardo a
CQRS and event sourcing

2. about me
{
"firstName": "Alessandro",
"lastName": "Melchiori",
"role": "software architect @ codiceplastico",
"contacts": [
{ "type": "email", "value": alessandro@codiceplastico.com },
{ "type": "twitter", "value": "@amelchiori" },
{ "type": "blog", "value": http://blog.codiceplastico.com/melkio }
]
}

3. Il contesto
• Applicazione finanziaria (non “always online”)
• Circa 70 utenti
• 250.000+ aziende
• 750.000+ bilanci
• 70.000.000+ voci di bilancio
• 16.000+ call/mese
• “Pluggato” a servizi di terze parti
• Picchi di lavoro “temporali” (…la nuvola può darci una mano)

4. Agenda
• Com’era
• Com’è
• Come sarà

5. Presentation Layer
Come era…
Service/Application Layer
Domain Model
Storage

6. Come era…

7. Come era…

8. Come era…

9. I problemi…
• Logica (mal) sparpagliata
• Contesti non definiti
• Modello “fragile” e poco propenso alle evoluzioni
• Un unico modello per la lettura e per la scrittura
• Prestazioni
• UI “generazionalista”

10. DDD: brevi cenni
• Use AGGREGATES as unit of consistency across your domain
model
• Protect your model with clearly defined BOUNDED CONTEXT
(Eric Evans)
BC 01 BC 02 BC 03

11. DDD: brevi cenni
• It’s really become clear to me in the last couple of years that we
need a new building block and that is the Domain Events
(Eric Evans)
BC 01 BC 02 BC 03

12. CQRS / ES: brevi cenni
• Every method should either be a command that performs an
action, or a query that returns data to the caller, but NOT BOTH
(Bertrand Meyer)

13. CQRS / ES: brevi cenni
• A single model cannot be appropriate for reporting, searching
and transactional behavior
• State transition are an important part of our problem space and
should be modeled within our domain
(Greg Young, 2008)

14. L’evoluzione

15. Presentation Layer
Come è…
Service Layer
Read storage Domain Model
Write storage

16. Come sarà…
Worker / Web Role
Service Bus
ACS
AZURE ?
Blob Storage MongoDb
(PaaS or SaaS)

17. Quando
DDD/CQRS/ES
fanno per me?
Chiedilo al «tuo» UBIQUITOUS LANGUAGE
(Alessandro Melchiori)

18. Quando
DDD/CQRS/ES
fanno per me?
Tackling Complexity in the Heart of Software