🏗️ Architecture
CQRS Pattern
Command Query Responsibility Segregation in Gauzy.
Overview
CQRS separates read and write operations into different models. Gauzy uses NestJS's @nestjs/cqrs module for complex domain operations.
Architecture
Diagram source
graph LR
Client --> Controller
subgraph Write Side
Controller -->|Command| CH[Command Handler]
CH --> Service[Domain Service]
Service --> DB[(Database)]
end
subgraph Read Side
Controller -->|Query| QH[Query Handler]
QH --> ReadModel[Read Model]
ReadModel --> DB
end
CH -->|Event| EB[Event Bus]
EB --> EH1[Event Handler 1]
EB --> EH2[Event Handler 2]Commands
// Command definition
export class CreateTimerCommand {
constructor(
public readonly input: ITimerToggleInput,
public readonly requestContext: RequestContext,
) {}
}
// Command handler
@CommandHandler(CreateTimerCommand)
export class CreateTimerHandler implements ICommandHandler<CreateTimerCommand> {
async execute(command: CreateTimerCommand): Promise<ITimeLog> {
const { input, requestContext } = command;
// Business logic here
return this.timeLogService.create(input);
}
}Queries
// Query definition
export class GetTimerStatusQuery {
constructor(public readonly employeeId: string) {}
}
// Query handler
@QueryHandler(GetTimerStatusQuery)
export class GetTimerStatusHandler implements IQueryHandler<GetTimerStatusQuery> {
async execute(query: GetTimerStatusQuery): Promise<ITimerStatus> {
return this.timerService.getStatus(query.employeeId);
}
}Events
// Event
export class TimerStartedEvent {
constructor(public readonly timeLog: ITimeLog) {}
}
// Event handler
@EventsHandler(TimerStartedEvent)
export class TimerStartedHandler implements IEventHandler<TimerStartedEvent> {
handle(event: TimerStartedEvent) {
// Side effects: notifications, activity log, WebSocket broadcast
this.notificationService.notify(event.timeLog.employeeId, "Timer started");
this.wsGateway.emit("timer:started", event.timeLog);
}
}When to Use CQRS
| Use CQRS | Use Simple CRUD |
|---|---|
| Complex business logic | Simple data operations |
| Multiple side effects | No side effects |
| Event-driven workflows | Basic CRUD |
| Audit trail required | Low complexity |
Related Pages
- Service Layer Patterns — service architecture
- Event Bus Architecture — events
- Background Jobs — async processing