{ "title": "CQRS Pattern", "description": "Command Query Responsibility Segregation pattern with separate read and write models", "type": "architecture-pattern", "data": { "nodes": [ { "id": "query-get-user", "type": "query", "position": { "x": 50, "y": 100 }, "data": { "mode": "full", "message": { "id": "get-user-query", "name": "GET /users/{id}", "version": "1.0.0", "summary": "Query to retrieve user information from read model" }, "editor": { "title": "Query", "subtitle": "Edit the details of the query", "schema": { "type": "object", "required": ["message", "mode"], "properties": { "message": { "type": "object", "required": ["name", "version"], "properties": { "name": {"type": "string", "title": "Name", "default": "Random value", "description": "The name of the service"}, "version": {"type": "string", "title": "Version", "default": "1.0.0", "description": "The version number (e.g., 1.0.0)", "pattern": "^\\\\d+\\\\.\\\\d+\\\\.\\\\d+(?:-[\\\\w.-]+)?(?:\\\\+[\\\\w.-]+)?$"}, "summary": 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"^\\\\d+\\\\.\\\\d+\\\\.\\\\d+(?:-[\\\\w.-]+)?(?:\\\\+[\\\\w.-]+)?$"}, "summary": {"type": "string", "title": "Summary", "default": "", "description": "A brief summary of the command"} } } } } } }, "measured": {"width": 262, "height": 98}, "selected": false, "dragging": false }, { "id": "service-query-handler", "type": "service", "position": { "x": 400, "y": 100 }, "data": { "mode": "full", "service": { "id": "query-handler", "name": "Query Handler", "owners": ["read-team"], "sends": [], "receives": ["GetUser", "GetUserList"], "version": "1.0.0", "summary": "Handles read queries and returns data from read model" }, "editor": { "title": "Service", "subtitle": "Edit the details of the service", "schema": { "type": "object", "required": ["service", "mode"], "properties": { "service": { "type": "object", "required": ["name", "version"], "properties": { "name": {"type": "string", "title": "Name", "default": "Random value", "description": "The name of the service"}, "version": {"type": 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["Database", "Cache", "Queue", "File System", "Data Lake", "Data Warehouse"]} } } } } } }, "measured": {"width": 262, "height": 98}, "selected": false, "dragging": false }, { "id": "event-user-created", "type": "event", "position": { "x": 1100, "y": 250 }, "data": { "mode": "full", "message": { "id": "user-created-event", "name": "UserCreated", "version": "1.0.0", "summary": "Domain event published after successful user creation" }, "editor": { "title": "Event", "subtitle": "Edit the details of the event", "schema": { "type": "object", "required": ["message", "mode"], "properties": { "message": { "type": "object", "required": ["name", "version"], "properties": { "name": {"type": "string", "title": "Name", "default": "Random value", "description": "The name of the event"}, "version": {"type": "string", "title": "Version", "default": "1.0.0", "description": "The version number (e.g., 1.0.0)", "pattern": "^\\\\d+\\\\.\\\\d+\\\\.\\\\d+(?:-[\\\\w.-]+)?(?:\\\\+[\\\\w.-]+)?$"}, "summary": {"type": "string", "title": "Summary", "default": "", "description": "A brief summary of the event"} } } } } } }, "measured": {"width": 262, "height": 98}, "selected": false, "dragging": false }, { "id": "service-projection", "type": "service", "position": { "x": 1100, "y": 50 }, "data": { "mode": "full", "service": { "id": "projection-service", "name": "Projection Service", "owners": ["read-team"], "sends": [], "receives": ["UserCreated", "UserUpdated", "UserDeleted"], "version": "1.0.0", "summary": "Updates read models based on domain events from write side" }, "editor": { "title": "Service", "subtitle": "Edit the details of the service", "schema": { "type": "object", "required": ["service", "mode"], "properties": { "service": { "type": "object", "required": ["name", "version"], "properties": { "name": {"type": "string", "title": "Name", "default": "Random value", "description": "The name of the service"}, "version": {"type": "string", "title": "Version", "default": "1.0.0", "description": "The version number (e.g., 1.0.0)", "pattern": "^\\\\d+\\\\.\\\\d+\\\\.\\\\d+(?:-[\\\\w.-]+)?(?:\\\\+[\\\\w.-]+)?$"}, "summary": {"type": "string", "title": "Summary", "default": "", "description": "A brief summary of the service"} } } } } } }, "measured": {"width": 262, "height": 98}, "selected": false, "dragging": false }, { "id": "note-cqrs-instructions", "type": "note", "position": { "x": 50, "y": 450 }, "data": { "text": "āš” **CQRS Pattern**\n\nCommand Query Responsibility Segregation - separate read and write models:\n\n**šŸ“– Read Side:** **Queries** ā†’ **Query Handler** ā†’ **Read Model (MongoDB)**\n**āœļø Write Side:** **Commands** ā†’ **Command Handler** ā†’ **Write Model (PostgreSQL)** ā†’ **Events** ā†’ **Projections**\n\n**Key Benefits:**\nā€¢ **Optimized models** - Read/write databases optimized for their use cases\nā€¢ **Scalability** - Independent scaling of read and write workloads\nā€¢ **Flexibility** - Different technologies for different needs\nā€¢ **Complex queries** - Rich read models with denormalized views\n\n**How it works:**\n1. **Commands** modify state via Command Handler\n2. **Write Model** stores normalized data\n3. **Domain Events** published after state changes\n4. **Projection Service** updates Read Models\n5. **Queries** served from optimized Read Models\n\n**šŸ’” Pro tip:** Start simple - add CQRS when read/write patterns diverge significantly!", "color": "orange" }, "measured": {"width": 350, "height": 280}, "selected": false, "dragging": false, "width": 350, "height": 280, "resizing": false } ], "edges": [ { "source": "query-get-user", "target": "service-query-handler", "label": "Query Request", "markerEnd": {"type": "arrowclosed", "color": "#000000"}, "animated": false, "type": "default", "data": {"source": "query", "target": "service", "message": {"collection": "queries", "opacity": 1}}, "id": "xy-edge__query-get-user-service-query-handler" }, { "source": "command-create-user", "target": 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"xy-edge__service-command-handler-data-write-model" }, { "source": "service-command-handler", "target": "event-user-created", "label": "Publishes", "markerEnd": {"type": "arrowclosed", "color": "#000000"}, "animated": true, "type": "animatedMessage", "data": {"source": "service", "target": "event", "message": {"collection": "events", "opacity": 1}}, "id": "xy-edge__service-command-handler-event-user-created" }, { "source": "event-user-created", "target": "service-projection", "label": "Consumed by", "markerEnd": {"type": "arrowclosed", "color": "#000000"}, "animated": true, "type": "animatedMessage", "data": {"source": "event", "target": "service", "message": {"collection": "events", "opacity": 1}}, "id": "xy-edge__event-user-created-service-projection" }, { "source": "service-projection", "target": "data-read-model", "label": "Updates", "markerEnd": {"type": "arrowclosed", "color": "#000000"}, "animated": false, "type": "default", "data": {"source": "service", "target": "data", "message": {"collection": "data", "opacity": 1}}, "id": "xy-edge__service-projection-data-read-model" } ], "viewport": {"x": 50, "y": 50, "zoom": 0.7}, "creationDate": "2025-01-01T00:00:00.000Z", "name": "CQRS Pattern", "version": "1.0.0", "source": "https://eventcatalog.dev", "appState": {}, "id": "cqrs-pattern" }, "usecase": "Design CQRS Architecture", "mermaid": "flowchart LR\n Q[Query] --> QH[Query Handler]\n QH --> R[(Read DB)]\n C[Command] --> CH[Command Handler]\n CH --> W[(Write DB)]\n CH --> E[Events]", "tags": ["Data Management"] }