Loading MQ::STREAM...
“Instead of storing only current state (e.g. Balance = $150), Event Sourcing stores every state-changing event (AccountOpened, MoneyDeposited, FeeCharged). Command Query Responsibility Segregation (CQRS) uses these event streams to build high-speed read projections in Elasticsearch or Redis.”
Store state as a sequence of immutable domain events and project read models asynchronously.
// Event Sourcing Aggregate Reconstitution
class BankAccountAggregate {
balance = 0;
status = 'INITIAL';
apply(event) {
switch (event.type) {
case 'AccountOpened':
this.status = 'ACTIVE';
break;
case 'MoneyDeposited':
this.balance += event.amount;
break;
case 'MoneyWithdrawn':
this.balance -= event.amount;
break;
}
}
}Snapshots stored every 1,000 events prevent replaying years of events when loading an aggregate into memory.