Health check pattern in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of a health check in microservices?

In a microservices architecture, why do we implement health checks?

A To automatically update the service's code

B To increase the service's processing speed

C To store user data securely

D To monitor if a service is running and responsive

💡 Hint

Think about what helps keep the system reliable by knowing if parts are working.

Health checks help detect if a service is alive and able to respond, which is crucial for system reliability.

❓ Architecture

intermediate

Which component typically performs health checks in a microservices system?

In a microservices setup, who usually initiates health checks to verify service status?

A The service itself periodically checks its own health

B An external monitoring system or load balancer

C The database server connected to the service

D The client application making requests

💡 Hint

Consider who needs to know if a service is healthy to route traffic properly.

External systems like load balancers or monitoring tools perform health checks to decide if a service should receive traffic.

❓ scaling

advanced

How does health check frequency affect system scalability?

What is the impact of setting very frequent health checks on a microservices system?

A It can increase network and CPU load, potentially reducing scalability

B It reduces the number of service instances needed

C It has no impact on system resources or scalability

D It always improves scalability by detecting failures faster

💡 Hint

Think about how often checking status uses resources.

Very frequent health checks increase resource usage, which can reduce the system's ability to scale efficiently.

❓ tradeoff

advanced

What is a tradeoff when choosing between simple and deep health checks?

Choosing between a simple ping check and a deep check (database, dependencies) involves what tradeoff?

A Deep checks never fail; simple checks cause false alarms

B Simple checks always detect all failures; deep checks are unnecessary

C Simple checks are faster but may miss hidden failures; deep checks are slower but more accurate

D There is no difference; both provide the same information

💡 Hint

Consider speed versus thoroughness.

Simple checks quickly confirm if a service responds but may miss internal issues. Deep checks take longer but verify full functionality.

❓ estimation

expert

Estimate the network overhead of health checks in a system with 1000 services checking every 30 seconds

Each health check request and response is 1 KB. How much network data is used per minute by all services combined?

A 2000 KB per minute

B 200 KB per minute

C 120 KB per minute

D 100 KB per minute

💡 Hint

Calculate requests per minute and multiply by data size.

Each service sends 2 checks per minute (60/30). 1000 services × 2 checks × 1 KB (request + response) = 2000 KB per minute.

Practice

1. What is the main purpose of the health check pattern in microservices?

easy

A. To regularly verify if a service is running and responsive

B. To increase the size of the service database

C. To encrypt communication between services

D. To deploy new versions of the service automatically

Solution

1. Step 1: Understand the health check pattern purpose

   The health check pattern is designed to monitor if a microservice is alive and functioning properly by sending simple requests to it.

2. Step 2: Identify the correct purpose among options

   Only To regularly verify if a service is running and responsive describes this monitoring function, while others describe unrelated tasks like database size, encryption, or deployment.

3. Final Answer:

   To regularly verify if a service is running and responsive -> Option A

4. Quick Check:

   Health check = verify service status [OK]

Hint: Health check means checking if service is alive and working [OK]

Common Mistakes:

• Confusing health check with deployment or encryption
• Thinking health check changes service data
• Assuming health check increases service capacity

2. Which of the following is the correct way to implement a health check endpoint in a microservice?

easy

A. Create an endpoint like /health that returns status 200 if service is healthy

B. Create an endpoint that deletes all data when called

C. Create an endpoint that returns service logs only

D. Create an endpoint that restarts the service automatically

Solution

1. Step 1: Identify typical health check endpoint behavior

   A health check endpoint usually responds with a simple status code like 200 OK to indicate the service is healthy.

2. Step 2: Match this behavior with the options

   Create an endpoint like /health that returns status 200 if service is healthy matches this by returning status 200 on /health. Other options perform unrelated or harmful actions.

3. Final Answer:

   Create an endpoint like /health that returns status 200 if service is healthy -> Option A

4. Quick Check:

   Health endpoint = status 200 OK [OK]

Hint: Health endpoint returns 200 OK if service is fine [OK]

Common Mistakes:

• Confusing health check with data deletion
• Expecting health check to return logs
• Assuming health check restarts service

3. Consider this pseudocode for a health check endpoint:

function healthCheck() {
  if (database.isConnected() && cache.isAvailable()) {
    return { status: 200, message: 'Healthy' };
  } else {
    return { status: 503, message: 'Unhealthy' };
  }
}

What will the endpoint return if the database is connected but the cache is down?

medium

A. An error is thrown

B. { status: 200, message: 'Healthy' }

C. { status: 404, message: 'Not Found' }

D. { status: 503, message: 'Unhealthy' }

Solution

1. Step 1: Analyze the condition in the healthCheck function

   The function returns healthy only if both database.isConnected() and cache.isAvailable() are true.

2. Step 2: Evaluate the given scenario

   Database is connected (true), cache is down (false), so the condition is false and the function returns status 503 with 'Unhealthy'.

3. Final Answer:

   { status: 503, message: 'Unhealthy' } -> Option D

4. Quick Check:

   Both checks true = 200, else 503 [OK]

Hint: Both dependencies must be healthy for 200 OK [OK]

Common Mistakes:

• Assuming partial health returns 200 OK
• Confusing 503 with 404 status
• Expecting an error instead of status response

4. A microservice health check endpoint is implemented as follows:

GET /health
Response: { "status": "ok" }

But monitoring tools report the service as unhealthy. What is the likely problem?

medium

A. The service is actually down and not responding

B. The endpoint does not return an HTTP status code 200

C. The endpoint URL should be /status instead of /health

D. The response body is missing the word 'healthy'

Solution

1. Step 1: Understand monitoring tool expectations

   Most monitoring tools expect the health check endpoint to return HTTP status code 200 to mark service healthy.

2. Step 2: Identify the issue with the current implementation

   The response body contains status 'ok' but if the HTTP status code is not 200, tools may mark it unhealthy.

3. Final Answer:

   The endpoint does not return an HTTP status code 200 -> Option B

4. Quick Check:

   Health check needs HTTP 200 status [OK]

Hint: Health check must return HTTP 200 status code [OK]

Common Mistakes:

• Thinking response body text controls health status
• Assuming endpoint URL name matters
• Ignoring actual service availability

5. You design a microservice system with multiple services. To improve reliability, you want to implement health checks that also verify database and cache connectivity. Which approach best follows the health check pattern?

hard

A. Each service exposes a /health endpoint that always returns 200 regardless of dependency status

B. Only one central service exposes a health check endpoint for all services combined

C. Each service exposes a /health endpoint that returns 200 only if all dependencies (database, cache) are reachable; otherwise returns 503

D. Health checks are done by querying the database directly without service endpoints

Solution

1. Step 1: Understand health check pattern for dependencies

   Health checks should verify the service and its critical dependencies like database and cache to ensure full functionality.

2. Step 2: Evaluate the options for best practice

   Each service exposes a /health endpoint that returns 200 only if all dependencies (database, cache) are reachable; otherwise returns 503 correctly implements a health endpoint that returns 200 only if all dependencies are healthy, otherwise 503. This supports automatic recovery and monitoring.

3. Final Answer:

   Each service exposes a /health endpoint that returns 200 only if all dependencies (database, cache) are reachable; otherwise returns 503 -> Option C

4. Quick Check:

   Health check includes dependencies, returns 200 or 503 [OK]

Hint: Health check must verify all critical dependencies [OK]

Common Mistakes:

• Ignoring dependency status in health check
• Relying on a single central health endpoint
• Checking dependencies outside service endpoints