A system with thousands of event types Our work at AFAS Software

Michiel Lead Software Architect @ AFAS Software [email protected] @michielovereem https://movereem.nl Overeem

500+ employees (4 locations) 12.000 customers (companies) AFAS Software 500+ employees (4 locations)

AFAS Profit

Small business and accountants AFAS SB+ 500+ employees (4 locations)

How do we move from Profit to SB+?

Person Entity Customer Role Order Agreement party Spending limit Address Organisation Entity Delivery BusinessAc tivity party Invoice BusinessAc tivity party Address Address Spending limit Spending limit Own Organisation Workarea workarea Spending limit

Person Entity Customer Role Order Agreement party Spending limit Address Organisation Entity Delivery BusinessAc tivity party Invoice BusinessAc tivity party Address Address Spending limit Spending limit Own Organisation Workarea workarea Spending limit • Functional model • Only suitable for ERP • Variability in the model • Contains 25 years of knowledge 22 25 96

Person Entity Customer Role Order Agreement party Spending limit Address Organisation Entity Delivery BusinessAc tivity party Invoice BusinessAc tivity party Address Address Spending limit Spending limit Own Organisation Workarea workarea Spending limit Generate ERP software

Person Entity Customer Role Order Agreement party Spending limit Address Organisation Entity Delivery BusinessAc tivity party Invoice BusinessAc tivity party Address Address Spending limit Spending limit Own Organisation Workarea workarea Spending limit

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query Plain and simple CQRS & event sourcing

StreamItem Aggregate StreamItem Aggregate StreamItem Aggregate Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1; Id=C) Event (Nr=1; Id=B) Event (Nr=1; Id=A) Query Event (Nr=1; Id=1) Event (Nr=1; Id=2) Event (Nr=2; Id=1) Aggregate Aggregate Aggregate StreamItem Aggregate Data QueryModel Object Data QueryModel Object EventHandler Projector Data QueryModel Object Data QueryModel Object Query Command

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query 3687 11646 4915 1377 1050

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Event Store stats 34.106.336 events from 3469 event types Started with 8 customers, currently at 91 customers 0,00 5.000.000,00 10.000.000,00 15.000.000,00 20.000.000,00 25.000.000,00 30.000.000,00 35.000.000,00 40.000.000,00 Total # of events

Person Entity Customer Role Order Agreement party Spending limit Address Organisation Entity Delivery BusinessAc tivity party Invoice BusinessAc tivity party Address Address Spending limit Spending limit Own Organisation Workarea workarea Spending limit A change here Or here … Or here … Impact!

V1.1 V1.2

V1.1

V1.1 V1.2

V1.1 V1.2

V1.1 V1.2

V1.2

V1.1 V1.2 This is where the magic happens…

Repair/Upgrade scripts Default data Event rewrites Query StreamItem UpgradeScript Command Command StreamItem … Command

Some additional patterns…

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query StreamItem ProcessManager Event (Nr=1) Event (Nr=2) Event (Nr=3) Command EventHandler Router ProcessManagers

EventHandler StreamProjector Data QueryModel Object Data QueryModel Object Data QueryModel Object Query StreamItem Aggregate Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Data QueryModel Object EventHandler Projector Query Event (Nr=1) Event (Nr=2) Event (Nr=3) StreamProjectors

Data QueryModel Object EventHandler Projector Event (Nr=1; Id=C) Event (Nr=1; Id=B) Event (Nr=1; Id=A) Query Event (Nr=1; Id=1) Event (Nr=1; Id=2) Event (Nr=2; Id=1) Data QueryModel Object Data QueryModel Object EventHandler Projector Data QueryModel Object Data QueryModel Object Query Cross-Projector-Joins

Data QueryModel Object EventHandler Projector Event (Nr=1; Id=C) Event (Nr=1; Id=B) Event (Nr=1; Id=A) Query Event (Nr=1; Id=1) Event (Nr=1; Id=2) Event (Nr=2; Id=1) Data QueryModel Object EventHandler Projector Data QueryModel Object Query

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query Direct command results

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query Push notifications from projectors

Data QueryModel Object EventHandler Projector Event (Nr=1; Id=C) Event (Nr=1; Id=B) Event (Nr=1; Id=A) Query Data QueryModel Object EventHandler Projector Data QueryModel Object Query Timers & Projectors-on-projectors

Data QueryModel Object StreamItem Aggregate EventHandler Projector Command Event (Nr=1) Event (Nr=2) Event (Nr=3) Query StreamItem ProcessManager Event (Nr=1) Event (Nr=2) Event (Nr=3) Command EventHandler Router Parallel & low-priority event processing

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Sync events

[email protected] @michielovereem https://movereem.nl Low-code / Impact analysis / Upgrade process / Several specific patterns Person Entity Customer Role Order Agreement party Spending limit Address Organisation Entity Delivery BusinessAc tivity party Invoice BusinessAc tivity party Address Address Spending limit Spending limit Own Organisation Workarea workarea Spending limit