Bounded context mapping in Microservices - Architecture Diagram

System Overview - Bounded context mapping

This system demonstrates how bounded contexts in a microservices architecture are mapped and interact. Each bounded context represents a distinct domain with its own data and logic, communicating through well-defined interfaces. The key requirement is to maintain clear boundaries to avoid data conflicts and enable independent service evolution.

Architecture Diagram

User
  |
  v
+----------------+
| API Gateway    |
+----------------+
  |          |
  v          v
+---------+  +---------+
| Order   |  | Payment |
| Service |  | Service |
+---------+  +---------+
  |            |
  v            v
+---------+  +---------+
| Order   |  | Payment |
| DB      |  | DB      |
+---------+  +---------+

Legend:
- API Gateway routes requests
- Order Service handles order domain
- Payment Service handles payment domain
- Each service has its own database
- Services communicate asynchronously via message queue

+----------------+
| Message Queue  |
+----------------+
       ^
       |
+----------------+
| Shipping       |
| Service        |
+----------------+
       |
       v
+----------------+
| Shipping DB    |
+----------------+

Components

User

user

End user interacting with the system

API Gateway

api_gateway

Routes user requests to appropriate services

Order Service

service

Manages order domain logic and data

Payment Service

service

Manages payment domain logic and data

Shipping Service

service

Handles shipping domain logic and data

Order DB

database

Stores order data for Order Service

Payment DB

database

Stores payment data for Payment Service

Shipping DB

database

Stores shipping data for Shipping Service

Message Queue

message_queue

Enables asynchronous communication between services

Request Flow - 10 Hops

User → API Gateway

API Gateway → Order Service

Order Service → Order DB

Order Service → Message Queue

Message Queue → Payment Service

Payment Service → Payment DB

Payment Service → Message Queue

Message Queue → Shipping Service

Shipping Service → Shipping DB

Shipping Service → User

Failure Scenario

Component Fails:Message Queue

Impact:Asynchronous communication between services stops; Payment and Shipping services do not receive events, causing delays and inconsistent state.

Mitigation:Implement message queue replication and persistence; use fallback retries and alerting to restore message flow quickly.

Architecture Quiz - 3 Questions

Which component is responsible for routing user requests to the correct service?

A Message Queue

B API Gateway

C Order Service

D Load Balancer

Design Principle

This architecture shows how bounded contexts separate domain logic and data into distinct microservices. Each service owns its data and communicates asynchronously to maintain loose coupling and scalability.

Practice

1. What is the main purpose of bounded context mapping in microservices architecture?

easy

A. To divide a system into clear, manageable parts with defined boundaries

B. To merge all services into a single large application

C. To increase the number of database tables in a system

D. To remove communication between different teams

Solution

1. Step 1: Understand bounded context concept

   Bounded context means splitting a system into parts that have clear boundaries and responsibilities.

2. Step 2: Identify the main goal of mapping

   Mapping helps teams work independently and reduces complexity by defining these boundaries.

3. Final Answer:

   To divide a system into clear, manageable parts with defined boundaries -> Option A

4. Quick Check:

   Bounded context = clear system parts [OK]

Hint: Bounded context means clear boundaries in system parts [OK]

Common Mistakes:

• Thinking bounded context merges services
• Confusing bounded context with database design
• Assuming it removes team communication

2. Which of the following correctly represents a relationship type in bounded context mapping?

easy

A. Customer/Supplier means contexts never communicate

B. Shared Kernel means two contexts share a small part of their domain model

C. Open Host Service means one context copies all data from another context

D. Conformist means contexts ignore each other's models completely

Solution

1. Step 1: Review relationship types in bounded context mapping

   Shared Kernel means two contexts share a small, common part of their domain model to stay consistent.

2. Step 2: Check other options for correctness

   Open Host Service is about providing a stable interface, not copying all data. Customer/Supplier implies communication. Conformist means one context adapts to another's model, not ignoring it.

3. Final Answer:

   Shared Kernel means two contexts share a small part of their domain model -> Option B

4. Quick Check:

   Shared Kernel = shared small domain part [OK]

Hint: Shared Kernel means sharing a small model part [OK]

Common Mistakes:

• Confusing Open Host Service with data copying
• Thinking Customer/Supplier means no communication
• Believing Conformist ignores other models

3. Given two bounded contexts A and B where A is the Customer and B is the Supplier, what is the expected interaction pattern?

medium

A. Context B provides services that Context A consumes

B. Context A adapts to B's model without changes

C. Contexts A and B share the same database schema

D. Contexts A and B never exchange data or messages

Solution

1. Step 1: Understand Customer/Supplier relationship

   In this pattern, the Supplier context offers services or data that the Customer context uses.

2. Step 2: Analyze options

   Context A adapts to B's model without changes describes Conformist, not Customer/Supplier. Contexts A and B share the same database schema is incorrect because sharing the same database schema breaks bounded context boundaries. Contexts A and B never exchange data or messages contradicts the relationship.

3. Final Answer:

   Context B provides services that Context A consumes -> Option A

4. Quick Check:

   Customer/Supplier = Supplier provides services [OK]

Hint: Supplier provides, Customer consumes services [OK]

Common Mistakes:

• Mixing Customer/Supplier with Conformist
• Assuming shared database schema
• Thinking no data exchange happens

4. You have two bounded contexts with a Conformist relationship, but the Customer context is modifying the Supplier's domain model directly. What is the problem?

medium

A. The Conformist pattern requires sharing the same database schema

B. The Supplier context must always copy the Customer's model

C. Both contexts should merge into one to avoid conflicts

D. The Customer context should not change the Supplier's model; it should adapt to it

Solution

1. Step 1: Understand Conformist relationship rules

   In Conformist, the Customer context adapts to the Supplier's model but does not modify it directly.

2. Step 2: Identify the error in modifying Supplier's model

   Modifying the Supplier's model breaks the boundary and can cause inconsistencies.

3. Final Answer:

   The Customer context should not change the Supplier's model; it should adapt to it -> Option D

4. Quick Check:

   Conformist means adapt, not modify [OK]

Hint: Customer adapts Supplier model, does not modify it [OK]

Common Mistakes:

• Thinking Supplier copies Customer model
• Merging contexts unnecessarily
• Assuming shared database schema is required

5. You are designing a large e-commerce system with multiple teams. How should you apply bounded context mapping to ensure scalability and team independence?

hard

A. Ignore context boundaries and let teams decide data sharing ad hoc

B. Combine all domains into one large context to simplify communication

C. Define clear bounded contexts for domains like Orders, Payments, and Inventory, and map their relationships explicitly

D. Allow teams to share a single database schema to avoid data duplication

Solution

1. Step 1: Identify the need for clear domain boundaries

   Large systems benefit from dividing domains like Orders, Payments, and Inventory into separate bounded contexts.

2. Step 2: Map relationships explicitly for team independence

   Explicit mapping helps teams understand dependencies and communicate properly without tight coupling.

3. Step 3: Avoid combining domains or sharing schemas

   Combining domains or sharing schemas increases complexity and reduces scalability.

4. Final Answer:

   Define clear bounded contexts for domains like Orders, Payments, and Inventory, and map their relationships explicitly -> Option C

5. Quick Check:

   Clear contexts + explicit mapping = scalable teams [OK]

Hint: Clear contexts and explicit maps enable scalable teams [OK]

Common Mistakes:

• Merging all domains into one context
• Sharing a single database schema
• Ignoring boundaries and ad hoc sharing