Bounded Context (DDD series part 5)

Krzysztof Słomka
3 min readJan 15, 2023

Domain-Driven Design (DDD) is a powerful approach to software development that focuses on understanding the business domain and using that understanding to drive the design of software systems. One of the key building blocks of DDD is the concept of a Bounded Context. In this post, we will explore what a Bounded Context is, why it’s important, and how it can be used to improve the design of software systems.

A Bounded Context is a boundary within which a specific domain model applies. It defines a context within which a certain set of terms, concepts and rules make sense. The idea behind Bounded Context is to separate different parts of the system that have different models and different rules. This allows different parts of the system to evolve independently of one another and reduces the complexity of the overall system.

One of the key benefits of Bounded Contexts is that they help to manage complexity. By breaking down a system into smaller, more manageable parts, Bounded Contexts make it easier to understand and work with the system. Additionally, Bounded Contexts allow different parts of the system to evolve independently of one another, which can help to ensure that the system remains relevant and useful over time.

When creating Bounded Contexts, it’s important to involve domain experts as they are the ones who have the most knowledge and understanding of the business domain. They can help to identify the key concepts, relationships, and rules that govern each part of the system, which can improve the overall quality of the Bounded Contexts. Additionally, it’s important to use a common vocabulary and concepts when creating Bounded Contexts, which can help to create a shared understanding of the domain among developers and domain experts.

In practice, Bounded Contexts can be implemented as different modules in your application, each with its own database, services, and interfaces. In this way, you can ensure that each module is self-contained and only communicates with other modules through a well-defined interface. This makes it easier to change and evolve each module independently, without affecting the other parts of the system.

Imagine that the e-commerce application has several different components, such as an inventory management system, an order management system, and a customer management system. Each of these components has its own set of concepts, rules, and relationships.

Instead of trying to build one monolithic system that includes all of these components, we can use Bounded Contexts to separate these components into different parts of the system. For example, we can create a Bounded Context for the inventory management system, another for the order management system, and another for the customer management system.

In the inventory management Bounded Context, we can define concepts such as Product, Stock, Warehouse, and Inventory. The rules and relationships that govern this Bounded Context include how products are tracked, how stock levels are managed, and how warehouses are organized. This Bounded Context would have its own database, services, and interfaces that are specific to inventory management.

In the order management Bounded Context, we can define concepts such as Order, Customer, Payment, and Shipping. The rules and relationships that govern this Bounded Context include how orders are placed, how customers are billed, and how shipments are tracked. This Bounded Context would also have its own database, services, and interfaces that are specific to order management.

By using Bounded Contexts in this way, we can ensure that each part of the system is self-contained

In conclusion, Bounded Contexts are a powerful tool that can be used to improve the design of software systems. They help to manage complexity by breaking down a system into smaller, more manageable parts, and allow different parts of the system to evolve independently of one another. By involving domain experts, using a common vocabulary and concepts, and implementing Bounded Contexts as independent modules, organizations can ensure that their software systems are well-designed, maintainable, and easy to understand. Bounded Contexts provide a clear separation between different parts of the system, making it easier to manage complexity and evolve the system over time.

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Krzysztof Słomka

My name is Krzysztof, I'm a software architect and developer, with experience of leading teams and delivering large scalable projects for over 13 years...