# Architectural Decoupling Report ## PHASE 1: BOUNDED CONTEXT & COUPLING DIAGNOSIS **Core Domain Identification:** - Identity Domain: Manages profile metadata and user record updates. - Transaction Domain: Manages checkout transactions and order summaries. **Coupling Bottlenecks:** 1. **Direct Class Instantiation:** The ordering handler directly imports and calls internal methods from the user data service, preventing them from running on separate server instances. 2. **Shared Memory Context:** A single runtime error in the user profile verification block halts the entire execution stream of the payment processing sequence. ## PHASE 2: DECOUPLED ARCHITECTURE DESIGN **Domain Separation Strategy:** Establish two distinct Bounded Contexts: IdentityContext and OrderContext. Each module must encapsulate its own data layer definitions and execute inside independent deployment runtimes. **Inter-Service Communication:** Implement an asynchronous Event-Driven pattern. When an order completes, the Order service publishes an event notification to a messaging cluster, which the Identity service processes independently without blocking execution loops. ## PHASE 3: REFACTORING & DOMAIN SPLITTING ### Legacy Monolithic Implementation (Tightly Coupled Node.js) ```javascript // Monolithic implementation linking user logic directly into order flows const UserService = require("./UserService"); class OrderManager { async createOrder(userId, orderValue) { const user = await UserService.getUserProfile(userId); if (user.isActive) { const order = await db.query("INSERT INTO orders VALUES ($1)", userId); return order; } return null; } } ``` ### Decoupled Implementation (Isolated Domain Handlers) ```javascript // Clean Domain Separation: Order Domain Module using independent interfaces class OrderService { constructor(userValidationService) { this.userValidator = userValidationService; } async placeOrder(userId, orderValue) { // Validation handled via injected abstract service interface const isValid = await this.userValidator.isUserEligible(userId); if (isValid) { return db.query("INSERT INTO orders VALUES ($1)", userId); } throw new Error("Order creation rejected by domain validation rules"); } } ``` ## PHASE 4: MIGRATION PATH & DATA STRATEGY - **Migration Risk:** Splitting code domains while they still reference a single shared SQL physical table can lead to data deadlocks during peak concurrent writes. - **Programmatic Mitigation:** Introduce a logical API facade layer over the shared schema, forcing all data updates to route through explicit interface definitions before physically separating the database clusters.