Event Sourcing: The Best Ubiquitous Pattern You've Never Heard Of

Event Sourcing is powerful way to think about domain objects and transaction processing. Rather than persisting an object in it's current state, event sourcing instead writes an immutable log of deltas (domain events) to the database. from this set of events, an object's state is derived, at any point in the past, simply by replaying the event history sequentially. Event sourcing is a deceptively radical idea which challenges our contemporary notions about transaction processing, while also being a mature pattern with a long history. This talk will take a look at how event processing is used across a spectrum of use cases, including database engines and financial systems.

Transcript

1. Event  Sourcing   The  best  ubiquitous  pa5ern  you’ve  never  heard  of.     {  Name:  ‘Bryan  Reinero’,   Title:  ‘Developer  Advocate’,   Twi5er:  ‘@blimpyacht’,   Email:  ‘bryan@mongdb.com’  }  
2. Let’s  Build  a  Banking  App   h5p://media.liveaucLongroup.net/i/5900/8757795_1.jpg?v=8CC56CE3AAC0100  
3. Let’s  Build  a  Banking  App   User: A Balance: 427 User: B Balance: 550
4. Let’s  Build  a  Banking  App   User: A Balance: 427 User: B Balance: 550 +5   -­‐5  
5. Event  Sourcing  
6. Event  Sourcing   h5p://www.avanscoperta.it/en/training/cqrs-­‐event-­‐sourcing-­‐and-­‐applying-­‐domain-­‐driven-­‐design/  
7. Event  Sourcing   h5ps://media.licdn.com/media/p/5/005/09f/2d8/3c9f5a5.jpg  
8. Event  Sourcing   Command  Query  Responsibility  SegregaLon   (CQRS)  
9. +4   -­‐2   +5   +7   -­‐4   +9   -­‐3   -­‐6   +2   +1   +1   -­‐5   State  at  t(12)  =  9   Event  Sourcing  
10. +4   -­‐2   +5   +7   -­‐4   +9   -­‐3   -­‐6   +2   +1   +1   -­‐5   State  at  t(5)  =  10   Event  Sourcing  
11. +4   -­‐2   +5   +7   -­‐4   +9   -­‐3   -­‐6   +2   +1   +1   -­‐5   State  at  t(9)=  12   Event  Sourcing  
12. +4   -­‐2   +5   +7   -­‐4   +9   -­‐3   -­‐6   +2   +1   +1   -­‐5   Event  Sourcing   +5   -­‐4   +5  
13. Res  Gestae  Divi  AugusL  
17. 2ndary   Primary  
18. 2ndary   Primary  
19. 2ndary   Primary  
20. +4   -­‐2   +5   +7   -­‐4   +9   -­‐3   -­‐6   +2   +1   +1   -­‐5   Event  Sourcing  
21. +4   -­‐2   +5   +7   -­‐4   +9   -­‐3   -­‐6   +2   +1   +1   -­‐5   State  at  t(4)  =  14   Event  Sourcing   State  at  t(8)  =  10   State  at  t(12)  =  9  
23. Journal  
24. Journal   Ledger  
25. Accounts  Payable   Accounts  Receivable   Journal   Ledger  
26. Command  Query   Responsibility     SegregaLon  
27. CQRS  
28. CRUD  vs.  CQRS   U.I.   CRUD  
29. CRUD  vs.  CQRS   U.I.   WRITE   READ  
30. CRUD  vs.  CQRS   U.I.   WRITE   READ   Primary   READ  
31. CRUD  vs.  CQRS   U.I.   2ndary   WRITE   READ   2ndary   Primary   READ  
32. CRUD  vs.  CQRS   U.I.   2ndary   WRITE   READ   2ndary   Primary   READ  
33. Thanks!   {  Name:  ‘Bryan  Reinero’,   Title:  ‘Developer  Advocate’,   Twi5er:  ‘@blimpyacht’,   Email:  ‘bryan@mongdb.com’  }