Canary deployment in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main purpose of a canary deployment?

Imagine you have a new version of a microservice. You want to release it carefully to avoid breaking the whole system. What is the main goal of using a canary deployment?

A To test the new version with a small group of users before full release

B To release the new version to all users at once to save time

C To rollback the old version immediately after deployment

D To deploy the new version only in the development environment

💡 Hint

Think about reducing risk by limiting exposure.

Canary deployment releases the new version to a small subset of users first. This helps detect issues early before affecting everyone.

❓ Architecture

intermediate

Which component is essential for routing traffic in a canary deployment?

In a microservices system using canary deployment, which component is responsible for directing a portion of user requests to the new version while the rest go to the stable version?

A Logging and monitoring tool

B Database replication service

C Continuous integration server

D Load balancer with traffic splitting capability

💡 Hint

Think about how requests are distributed.

A load balancer that supports traffic splitting can route some requests to the new version and others to the stable version, enabling canary deployment.

❓ scaling

advanced

How should you scale the canary version during deployment?

You start a canary deployment by sending 5% of traffic to the new version. Over time, you want to increase this percentage. What is the best practice for scaling the canary version?

A Randomly change traffic percentages without monitoring

B Gradually increase traffic to the canary version while monitoring metrics

C Keep the canary version at 5% traffic indefinitely

D Immediately switch 100% traffic to the new version after deployment

💡 Hint

Think about risk and feedback.

Gradually increasing traffic allows detecting problems early and reduces risk. Monitoring metrics ensures stability before full rollout.

❓ tradeoff

advanced

What is a tradeoff when using canary deployment compared to blue-green deployment?

Canary and blue-green deployments are both strategies to release new versions. What is a key tradeoff when choosing canary deployment over blue-green?

A Canary deployment exposes only a small user group to risk but takes longer to fully release

B Canary deployment instantly switches all users to the new version

C Canary deployment requires more infrastructure than blue-green

D Canary deployment does not allow rollback

💡 Hint

Consider risk exposure and release speed.

Canary deployment reduces risk by exposing a small group first but takes more time to complete rollout compared to blue-green which switches all users at once.

❓ estimation

expert

Estimate the number of users affected during a canary deployment with 10 million daily users and 1% canary traffic

Your service has 10 million daily active users. You deploy a new version using canary deployment, routing 1% of traffic to it. How many users will experience the new version daily?

A 500,000 users

B 10,000 users

C 100,000 users

D 1,000,000 users

💡 Hint

Calculate 1% of 10 million.

1% of 10 million is 100,000 users who will see the canary version daily.

Practice

1. What is the main purpose of a canary deployment in microservices?

easy

A. To permanently run two versions side by side

B. To deploy all users to a new version at once

C. To release a new version to a small group of users first to reduce risk

D. To test the new version only in a development environment

Solution

1. Step 1: Understand the goal of canary deployment

   Canary deployment aims to reduce risk by releasing new software versions to a small subset of users first.

2. Step 2: Compare options with this goal

   To release a new version to a small group of users first to reduce risk matches this goal exactly, while others describe different deployment strategies.

3. Final Answer:

   To release a new version to a small group of users first to reduce risk -> Option C

4. Quick Check:

   Canary deployment = gradual rollout [OK]

Hint: Canary means small test group first, not all users [OK]

Common Mistakes:

• Confusing canary with blue-green deployment
• Thinking canary deploys to all users at once
• Assuming canary is only for testing environments

2. Which of the following is the correct way to control traffic during a canary deployment?

easy

A. Send 100% of traffic to the new version immediately

B. Route a small percentage of traffic to the new version and the rest to the old

C. Stop all traffic during deployment

D. Send traffic randomly without control

Solution

1. Step 1: Understand traffic control in canary deployment

   Traffic is gradually shifted to the new version to monitor its behavior safely.

2. Step 2: Identify the correct traffic routing method

   Route a small percentage of traffic to the new version and the rest to the old describes routing a small percentage to the new version while keeping most on the old version, which is correct.

3. Final Answer:

   Route a small percentage of traffic to the new version and the rest to the old -> Option B

4. Quick Check:

   Traffic control = gradual routing [OK]

Hint: Gradually shift traffic, never 100% at once [OK]

Common Mistakes:

• Sending all traffic immediately to new version
• Stopping traffic completely during deployment
• Ignoring traffic routing control

3. Consider this simplified code snippet for traffic routing in a canary deployment:

def route_request(user_id):
    if user_id % 10 == 0:
        return "new_version"
    else:
        return "old_version"

print(route_request(20))
print(route_request(23))

What will be the output?

medium

A. "new_version" followed by "old_version"

B. "new_version" followed by "new_version"

C. "old_version" followed by "old_version"

D. "old_version" followed by "new_version"

Solution

1. Step 1: Evaluate route_request(20)

   20 % 10 equals 0, so it returns "new_version".

2. Step 2: Evaluate route_request(23)

   23 % 10 equals 3, not 0, so it returns "old_version".

3. Final Answer:

   "new_version" followed by "old_version" -> Option A

4. Quick Check:

   Modulo 10 == 0 routes to new version [OK]

Hint: Check modulo condition carefully for routing [OK]

Common Mistakes:

• Misunderstanding modulo operator
• Assuming all users go to new version
• Mixing output order

4. A team implemented a canary deployment but noticed that 100% of users are routed to the new version immediately. What is the most likely cause?

medium

A. Traffic routing logic sends all traffic to new version without percentage control

B. Monitoring tools are not enabled

C. Rollback was triggered accidentally

D. Old version servers are down

Solution

1. Step 1: Analyze the symptom

   All users routed to new version immediately means no gradual traffic control.

2. Step 2: Identify the cause

   Traffic routing logic sends all traffic to new version without percentage control explains that routing logic lacks percentage control, causing full traffic shift.

3. Final Answer:

   Traffic routing logic sends all traffic to new version without percentage control -> Option A

4. Quick Check:

   Immediate full traffic = missing gradual routing [OK]

Hint: Check traffic routing code for percentage control [OK]

Common Mistakes:

• Blaming monitoring tools for routing issues
• Assuming rollback causes full traffic shift
• Ignoring server status impact

5. You want to design a canary deployment system that automatically rolls back if error rates exceed 5% during rollout. Which combination of components is essential?

hard

A. Load balancer, static routing, manual rollback process

B. Manual deployment script, user feedback form, database backup

C. Continuous integration server, code linter, version control

D. Traffic router, monitoring system, automated rollback controller

Solution

1. Step 1: Identify components for traffic control and monitoring

   A traffic router directs user requests between old and new versions; monitoring system tracks error rates.

2. Step 2: Include automated rollback for quick response

   An automated rollback controller triggers rollback if error thresholds are exceeded.

3. Final Answer:

   Traffic router, monitoring system, automated rollback controller -> Option D

4. Quick Check:

   Canary needs routing + monitoring + rollback [OK]

Hint: Combine routing, monitoring, and rollback for safe canary [OK]

Common Mistakes:

• Ignoring automation in rollback
• Confusing deployment tools with monitoring
• Missing traffic routing component