Single responsibility per service in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'Single responsibility per service' mean in microservices?

It means each microservice should focus on doing one specific job or task well, like a specialist in a team, rather than trying to do many things at once.

beginner

Why is having a single responsibility per service beneficial?

It makes services easier to understand, develop, test, and maintain. It also helps teams work independently and scale parts of the system separately.

intermediate

How does single responsibility per service improve system scalability?

Since each service handles one task, you can scale only the services that need more resources without affecting others, saving cost and improving performance.

intermediate

What is a common mistake when designing microservices related to responsibility?

Trying to put too many unrelated functions into one service, which makes it complex, hard to maintain, and less flexible.

beginner

Give a real-life example of single responsibility per service.

Imagine a food delivery app: one service handles user accounts, another handles orders, and another handles payments. Each service does one job well.

What is the main idea behind single responsibility per service?

A Each service should do one specific task.

B Each service should handle all tasks for a user.

C Services should share responsibilities equally.

D Services should be as large as possible.

Single responsibility means focusing each service on one task to keep it simple and manageable.

Which is a benefit of single responsibility per service?

A Harder to test services.

B Easier to scale individual services.

C More complex service dependencies.

D Slower development cycles.

Focusing services on one task allows scaling only the needed parts, improving efficiency.

What problem arises if a service has multiple responsibilities?

A It becomes less flexible and harder to update.

B It improves team independence.

C It reduces the number of services needed.

D It becomes easier to maintain.

Multiple responsibilities make a service complex and harder to change without affecting other parts.

In a microservices system, what should a payment service handle?

A User login and authentication.

B Sending marketing emails.

C Order tracking and delivery.

D Processing payments and transactions.

The payment service should focus only on payment-related tasks.

How does single responsibility per service affect team work?

A Teams share responsibility for all services equally.

B Teams must always coordinate on all services.

C Teams can work independently on different services.

D Teams cannot own a service fully.

Clear service boundaries let teams develop and deploy independently.

Explain the concept of single responsibility per service and why it matters in microservices.

Think about how dividing work into small focused parts helps a team.

Describe a simple example of a microservices system designed with single responsibility per service.

Use a real-life app like food delivery or online shopping.

Practice

1. What does the single responsibility principle mean in microservices?

easy

A. Services should be tightly coupled to improve performance.

B. Each service should handle multiple unrelated tasks.

C. Services should share the same database for all tasks.

D. Each service should do only one specific job.

Solution

1. Step 1: Understand the principle meaning

   Single responsibility means one service focuses on one task or job only.

2. Step 2: Evaluate options against this meaning

   Each service should do only one specific job. matches the principle exactly; others contradict it by mixing tasks or coupling.

3. Final Answer:

   Each service should do only one specific job. -> Option D

4. Quick Check:

   Single responsibility = One job per service [OK]

Hint: One service, one job keeps design simple and clear [OK]

Common Mistakes:

• Thinking one service can do many unrelated tasks
• Assuming shared databases mean single responsibility
• Confusing tight coupling with single responsibility

2. Which of the following is the correct way to name a microservice following single responsibility?

easy

A. UserManagementService

B. UserAndOrderService

C. Service123

D. DatabaseService

Solution

1. Step 1: Identify naming that reflects single responsibility

   The service name should clearly indicate one focused responsibility.

2. Step 2: Check options for clarity and focus

   UserManagementService clearly states it manages users only; others mix concerns or are vague.

3. Final Answer:

   UserManagementService -> Option A

4. Quick Check:

   Clear, focused name = single responsibility [OK]

Hint: Service name should reflect one clear job [OK]

Common Mistakes:

• Using vague or numeric names without meaning
• Combining multiple domains in one service name
• Naming services after infrastructure components

3. Given these microservices: UserService handles user data, OrderService handles orders. Which service should handle payment processing?

medium

A. UserService

B. PaymentService

C. OrderService

D. DatabaseService

Solution

1. Step 1: Analyze responsibilities of existing services

   UserService manages users, OrderService manages orders, so payment is a separate concern.

2. Step 2: Assign payment to a dedicated service

   Payment processing is a distinct responsibility, so PaymentService is appropriate.

3. Final Answer:

   PaymentService -> Option B

4. Quick Check:

   Separate payment = separate service [OK]

Hint: Separate distinct jobs into separate services [OK]

Common Mistakes:

• Assigning payment to unrelated services
• Combining payment with user or order logic
• Using generic service names that mix concerns

4. You find a microservice called InventoryAndShippingService causing deployment issues. What is the best fix following single responsibility?

medium

A. Merge it with UserService to reduce services

B. Add more features to InventoryAndShippingService

C. Split it into two services: InventoryService and ShippingService

D. Keep it as is and increase server resources

Solution

1. Step 1: Identify problem with combined responsibilities

   Inventory and shipping are two distinct jobs combined, causing complexity and deployment issues.

2. Step 2: Apply single responsibility by splitting services

   Splitting into InventoryService and ShippingService isolates concerns and simplifies management.

3. Final Answer:

   Split it into two services: InventoryService and ShippingService -> Option C

4. Quick Check:

   Split combined services to fix issues [OK]

Hint: Split combined services to fix complexity [OK]

Common Mistakes:

• Merging unrelated services increases complexity
• Adding features to overloaded services worsens problems
• Ignoring root cause and just adding resources

5. You are designing a microservices system for an online store. Which design best follows single responsibility per service?

hard

A. UserService, ProductService, OrderService, PaymentService, NotificationService

B. StoreService handling users, products, orders, payments, and notifications

C. UserService and OrderService only, handling all tasks

D. One big service for all store functions

Solution

1. Step 1: Understand the scope of each option

   UserService, ProductService, OrderService, PaymentService, NotificationService splits store functions into focused services; others combine many tasks.

2. Step 2: Match design to single responsibility principle

   UserService, ProductService, OrderService, PaymentService, NotificationService clearly assigns one responsibility per service, making it scalable and maintainable.

3. Final Answer:

   UserService, ProductService, OrderService, PaymentService, NotificationService -> Option A

4. Quick Check:

   One service, one job = UserService, ProductService, OrderService, PaymentService, NotificationService [OK]

Hint: Split big tasks into small focused services [OK]

Common Mistakes:

• Combining many tasks into one service
• Using too few services for complex domains
• Ignoring scalability and maintainability