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Bounded Context

A Bounded Context is a clearly delimited area within a system in which a domain model and its terms have a single, consistent meaning. It is the central structural principle from Domain-Driven Design (DDD) and the domain foundation for microservice boundaries.

Without explicit context boundaries, models emerge that try to be everything for everyone, are hard to maintain and lead to misunderstandings between teams.

Core concept

A Bounded Context defines:

  • Ubiquitous Language: Within the context, all terms have a precise, agreed meaning that is also visible in the code.
  • Model Boundaries: Outside the context, the model may look different without causing conflicts.
  • Team Responsibility: Each Bounded Context is owned by a single team (Conway's Law as an opportunity).

Context Mapping

The relationships between Bounded Contexts are visualised through Context Maps. Typical patterns:

  • Shared Kernel: Two teams share a common core model that both maintain.
  • Customer/Supplier: Upstream team provides the API, downstream team consumes it.
  • Anti-Corruption Layer (ACL): A protective layer that shields the own model from an external one.
  • Open Host Service: A published API for multiple consumers.

Focus: Deriving Microservice Boundaries from Domain Logic

Bounded Contexts prevent microservices from being split along technical layers (frontend/backend/DB) rather than along domain boundaries.

FAQ

Is a Bounded Context always the same as a microservice?

No. A Bounded Context is a domain concept; a microservice is a deployment artefact. In the early stages, a Bounded Context can live as a module within a monolith and be extracted later (Strangler Fig Pattern).

How large should a Bounded Context be?

Large enough for a single team to fully understand and own, but no larger. Aggregate count is context-dependent: it reflects domain language, model consistency boundaries, and cognitive load.

Reference Guide

Related topics

  • Methods: DDD, the domain method behind Bounded Context.
  • Methods, the methods section that frames Bounded Context.