Design Patterns MCP Server

{ "id": "cqrs", "name": "Command Query Responsibility Segregation", "category": "Architectural", "description": "Separates read and write operations using different models", "when_to_use": "Complex read/write patterns\nPerformance optimization\nEvent sourcing", "benefits": "Performance\nScalability\nFlexibility\nOptimized models", "drawbacks": "Increased complexity\nEventual consistency\nCode duplication", "use_cases": "High-performance systems\nEvent sourcing\nComplex reporting", "complexity": "High", "tags": [ "command-query", "performance", "segregation" ], "examples": { "typescript": { "language": "typescript", "code": "// CQRS: separate read and write models\n\n// Command Side (Write Model)\ninterface Command {\n execute(): Promise<void>;\n}\n\nclass CreateProductCommand implements Command {\n constructor(\n private id: string,\n private name: string,\n private writeDb: WriteDatabase\n ) {}\n \n async execute() {\n await this.writeDb.insert('products', { id: this.id, name: this.name });\n // Publish event for read model\n await eventBus.publish('ProductCreated', { id: this.id, name: this.name });\n }\n}\n\n// Query Side (Read Model - optimized for queries)\nclass ProductQuery {\n constructor(private readDb: ReadDatabase) {}\n \n async getProductById(id: string) {\n return this.readDb.query('SELECT * FROM product_view WHERE id = ?', [id]);\n }\n \n async searchProducts(term: string) {\n return this.readDb.query('SELECT * FROM product_search WHERE name LIKE ?', [`%${term}%`]);\n }\n}\n\n// Event Handler (syncs read model)\nclass ProductCreatedHandler {\n constructor(private readDb: ReadDatabase) {}\n \n async handle(event: any) {\n await this.readDb.insert('product_view', event);\n await this.readDb.insert('product_search', event);\n }\n}\n\n// Usage: separate paths for reads and writes\nconst command = new CreateProductCommand('1', 'Laptop', writeDb);\nawait command.execute();\n\nconst query = new ProductQuery(readDb);\nconst product = await query.getProductById('1');" } } }