event sourcing + cqrs

Event SourcingTHE BEST, UBIQUITOUS PATTERN

YOU’VE NEVER HEARD OF

@blimpyacht

5

User: ABalance: 427

User: BBalance: 550

User: ABalance: 427

User: BBalance: 550

User: ABalance: 427

User: BBalance: 550

+5-5

Event Sourcing

State

+4-2+5+7-4+9-3-6+2+1+1-5 t(12) = 9

Event Sourcing

+4-2+5+7-4+9-3-6+2+1+1-5

t(5) = 10

Event Sourcing

+4-2+5+7-4+9-3-6+2+1+1-5

t(9) = 12

Event Sourcing

+4-2+5+7-4+9-3-6+2+1+1-5

Event Sourcing

a = f ’(x)

+4-2+5+7-4+9-3-6+2+1+1-5

Event Sourcing

+5-4+5

Res Gestae Divi Augusti

2ndaryPrimary

2ndaryPrimary

2ndaryPrimary

+4-2+5+7-4+9-3-6+2+1+1-5

Event Sourcing

+4-2+5+7-4+9-3-6+2+1+1-5

t(4) = 14

Event Sourcing

t(8) = 10

t(12) = 9

+4-2+5+7-4+9-3-6+2+1+1-5

t(4) = 14

Event Sourcing

t(8) = 10

t(12) = 9

t’(4) = -2

t’(8) = -17

t’(12) = -22

{ _id: {

ts: 1213084687000, taxi: "abboip" }, loc: {

geometry: [ -122.39488, 37.75134

] }, fare: 0, ts: ISODate("2008-06-10T07:58:07Z")}

{ _id: ObjectId("56a4215a46778b69e08ff8ff"), taxi: "abboip", start: ISODate("2008-05-17T14:51:10Z"), route: { type: "LineString", coordinates: [ [ -122.39724, 37.74977 ], [ -122.40619, 37.74896 ], [ -122.41335, 37.74831 ], [ -122.414, 37.75157 ], [ -122.41438, 37.75552 ]

] }, end: ISODate("2008-05-17T14:55:58Z")}

Data Modeling Domain EventsDomain Objects

Accounts Payable

Accounts Payable

Accounts Receivable

Accounts Payable

Accounts Receivable

Journal

Accounts Payable

Accounts Receivable

Journal

Ledger

Command QueryResponsibility

Segregation

CQRS

CRUD vs. CQRS

CRUD

CRUD vs. CQRS

WRITE

READ

CRUD vs. CQRS

CRUD equals CQRS

WRITE

READ

READ

CRUD vs. CQRS

WRITE

READ

Variant Read Models: VIEWS

READREADREADREAD

WRITE

READ

Primary

READ

CRUD vs. CQRS

CRUD vs. CQRS

WRITE

READ

READ

Primary

2ndary

2ndary

Where it Gets Tricky

CRUD vs. CQRS

WRITE

READ

READ

Primary

2ndary

2ndary

CRUD vs. CQRS

WRITE

READ

READ

Primary

2ndary

2ndary

Consistent Replay+4-2+5+7-4+9-3-6+2+1+1-5

t(5) = 10 Exchange Rate Server

10 / 0.88 = 8.82€

Consistent Replay+4-2+5+7-4+9-3-6+2+1+1-5

t(5) = 10 Exchange Rate Server

10 / 0.87 = 8.70€

+4-2+5+7-4

+9-3-6+2+1+1-5

0.88 Exchange Rate Server

Consistent Replay

Where it Gets Trickier Still

External Updates+4-2+5+7-4+9-3-6+2+1+1-5

Notification

Subscriber

External Updates+4-2+5+7-4+9-3-6+2+1+1-5

Notification

Subscriber

Gaining Insight