This part establishes the starting point — a traditional, synchronous, and potentially monolithic Order Service.
1. Introduction: The Heart of E-commerce ❤️
Hook:
Start with a relatable scenario — the moment a user clicks “Place Order.”
Briefly introduce the Order Service as the mission-critical component that manages the lifecycle of a purchase.
Premise of the Series:
We’ll examine a classic implementation before transforming it into a modern, distributed system.
2. Anatomy of a Classic Order Service 🧩
Focus on Synchronicity
In a classic model, everything happens now and in-process.
The flow is straightforward:
OrderController → OrderService → InventoryService → PaymentService → ShippingService
Each call waits for an immediate response — a tightly coupled chain of synchronous operations.
Core Responsibilities
The traditional Order Service handles several critical tasks:
- Validation: Checking cart contents, stock availability, and user details.
- Persistence: Saving the order record (often in a relational database such as PostgreSQL or MySQL).
- Coordination: Making blocking calls to other services (Inventory, Payment, Shipping).
3. The Traditional Tech Stack 🧱
Architecture Overview
The Order Service architecture is designed as follows:
[Client] --> [Order Service API] --> [MongoDB]
|
v
[Kafka] --> [Consumers]
Client: Sends requests to the Order Service API.
Order Service API: Handles requests, processes orders, and interacts with MongoDB and Kafka.
MongoDB: Stores order data.
Kafka: Publishes OrderCreated events for downstream consumers.
Consumers: External systems or services that process Kafka events.
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