Health check endpoints in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a basic health check endpoint that returns a 200 status.

HLD

GET /health [1] 200 OK

Drag options to blanks, or click blank then click option'

Aresponds with

Breturns

Csends

Doutputs

Attempts:

3 left

💡 Hint

Common Mistakes

Using verbs that don't fit HTTP response context like 'responds with' instead of 'returns'.

Not returning any status code.

The health check endpoint should return a 200 OK status to indicate the service is healthy.

2fill in blank

medium

Complete the code to add a readiness check endpoint that verifies database connectivity.

HLD

if database.[1]():
    return 200
else:
    return 503

Drag options to blanks, or click blank then click option'

Aping

Bis_connected

Cconnect

Dcheck

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'connect' which attempts a new connection instead of checking existing connectivity.

Using generic names like 'check' without clear meaning.

The readiness check often uses a ping method to verify if the database is reachable.

3fill in blank

hard

Fix the error in the health check response code to correctly indicate service health.

HLD

def health_check():
    return 'Service is healthy', [1]

Drag options to blanks, or click blank then click option'

A200

B500

C404

D301

Attempts:

3 left

💡 Hint

Common Mistakes

Returning error codes like 404 or 500 which indicate problems.

Using redirect codes like 301 which are not appropriate here.

The health check should return HTTP status code 200 to indicate the service is healthy.

4fill in blank

hard

Fill both blanks to create a health check that returns JSON with status.

HLD

def health_check():
    return [1], [2]

Drag options to blanks, or click blank then click option'

A{"status": "ok"}

B200

C{'timestamp': time.time()}

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 404 status code which means not found.

Returning only timestamp without status.

The health check should return a JSON body with status and a 200 status code.

5fill in blank

hard

Fill all three blanks to implement a readiness check that returns 200 if cache and DB are healthy, else 503.

HLD

def readiness_check():
    if cache.[1]() and db.[2]():
        return [3]
    else:
        return 503

Drag options to blanks, or click blank then click option'

Aping

Bis_alive

C200

Dconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'connect' which may attempt new connections instead of health checks.

Returning 503 when services are healthy.

The readiness check calls ping on cache and is_alive on db, returning 200 if both are healthy.

Practice

1. What is the primary purpose of a health check endpoint in a system?

easy

A. To verify if the service is alive and functioning

B. To store user data securely

C. To handle user authentication

D. To serve static website content

Solution

1. Step 1: Understand the role of health check endpoints

   Health check endpoints are designed to tell if a service is alive and working properly.

2. Step 2: Identify the correct purpose among options

   Only To verify if the service is alive and functioning describes checking the service's health, while others describe unrelated functions.

3. Final Answer:

   To verify if the service is alive and functioning -> Option A

4. Quick Check:

   Health check = Verify service alive [OK]

Hint: Health checks confirm service status, not data or auth [OK]

Common Mistakes:

• Confusing health check with authentication
• Thinking health check stores data
• Assuming health check serves website content

2. Which URL path is commonly used for a readiness health check endpoint?

easy

A. /ready

B. /health

C. /status

D. /check

Solution

1. Step 1: Recall standard health check paths

   Readiness endpoints typically use the path /ready to indicate if the service is ready to accept traffic.

2. Step 2: Match the correct path

   Among the options, only /ready is the standard path for readiness checks.

3. Final Answer:

   /ready -> Option A

4. Quick Check:

   Readiness path = /ready [OK]

Hint: Readiness = /ready, Liveness = /health [OK]

Common Mistakes:

• Using /health for readiness instead of liveness
• Confusing /status or /check as standard paths
• Mixing readiness and liveness endpoints

3. Consider this pseudocode for a health check endpoint:

if database.isConnected() and cache.isAvailable():
    return 200
else:
    return 503

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

medium

A. 200

B. 503

C. 404

D. 500

Solution

1. Step 1: Analyze the condition logic

   The endpoint returns 200 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 condition fails and returns 503.

3. Final Answer:

   503 -> Option B

4. Quick Check:

   Both must be true for 200; else 503 [OK]

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

Common Mistakes:

• Assuming 200 if only one service is healthy
• Confusing 503 with 404 or 500
• Ignoring the AND condition in the code

4. A health check endpoint code snippet:

def health_check():
    if db.connected() or cache.available():
        return 200
    else:
        return 503

What is the main problem with this health check logic?

medium

A. It does not check any services

B. It returns 503 when both services are healthy

C. It returns 200 even if only one service is healthy

D. It uses incorrect HTTP status codes

Solution

1. Step 1: Understand the logical operator used

   The code uses OR, so it returns 200 if either db.connected() or cache.available() is true.

2. Step 2: Identify the issue with health check accuracy

   This means it reports healthy even if one service is down, which can mislead monitoring systems.

3. Final Answer:

   It returns 200 even if only one service is healthy -> Option C

4. Quick Check:

   OR allows partial health, which is incorrect [OK]

Hint: Use AND to ensure all services are healthy [OK]

Common Mistakes:

• Using OR instead of AND in health checks
• Ignoring partial failures in health status
• Misinterpreting HTTP status codes

5. You design a system with a /health endpoint for liveness and a /ready endpoint for readiness. Which of the following best describes when the /ready endpoint should return HTTP 503?

hard

A. When the service is completely down and unreachable

B. When the service is alive and ready to accept traffic

C. When the service is overloaded but still responding

D. When the service is alive but not ready to accept traffic due to missing dependencies

Solution

1. Step 1: Understand readiness vs liveness

   Liveness (/health) checks if service is alive; readiness (/ready) checks if it can handle requests safely.

2. Step 2: Identify readiness failure condition

   Readiness returns 503 if dependencies (like database) are missing, so service should not receive traffic yet.

3. Final Answer:

   When the service is alive but not ready to accept traffic due to missing dependencies -> Option D

4. Quick Check:

   Readiness 503 = alive but not ready [OK]

Hint: Ready means all dependencies OK; else 503 [OK]

Common Mistakes:

• Confusing liveness failure with readiness failure
• Returning 503 when service is fully down (should be liveness)
• Assuming overload means readiness failure