Incremental migration plan in Microservices - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the first step in an incremental migration plan.

Microservices

migration_steps = ['[1]', 'Build new services', 'Redirect traffic', 'Decommission old system']

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

AAnalyze current system

BTest new services

CRedirect traffic

DDeploy new services

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing deployment or testing as the first step.

The first step is to analyze the current system to understand dependencies and components before migration.

2fill in blank

medium

Complete the code to describe the purpose of building new services in migration.

Microservices

purpose = 'To [1] functionality from the monolith into independent services'

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

Adelay

Bremove

Ccombine

Dextract

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'combine' or 'remove' which do not fit the migration goal.

Building new services means extracting functionality from the monolith into smaller, independent services.

3fill in blank

hard

Fix the error in the migration step that redirects user traffic.

Microservices

def redirect_traffic(service):
    if service.status == 'ready':
        service.[1]('start')
    else:
        print('Service not ready')

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

Aswitch

Bactivate

Cstop

Dredirect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'stop' or 'redirect' which are not valid methods here.

The correct method to start handling traffic is 'activate', which enables the new service to receive requests.

4fill in blank

hard

Fill both blanks to complete the code that checks service readiness and switches traffic.

Microservices

if service.[1]() and system.[2]('all_services_ready'):
    system.switch_traffic_to(service)

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

Ais_ready

Bcheck_status

Cverify

Dis_active

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'verify' or 'is_active' which do not fit both blanks correctly.

Use 'is_ready()' to check if the service is ready and 'check_status' to verify system-wide readiness before switching traffic.

5fill in blank

hard

Fill all three blanks to complete the code that decommissions old services after migration.

Microservices

if service.[1]() and not system.[2](service) and service.[3] == 'inactive':
    system.decommission(service)

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

Ais_deprecated

Bis_referenced

Cstatus

Dis_ready

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing readiness with deprecation or referencing.

The code checks if the service is deprecated, not referenced elsewhere, and has status 'inactive' before decommissioning.

Practice

1. What is the main goal of an incremental migration plan in microservices?

easy

A. To avoid testing during migration

B. To rewrite the entire system at once

C. To remove all old services immediately

D. To move functionality step-by-step to reduce risk

Solution

1. Step 1: Understand migration goals

   Incremental migration aims to reduce risk by breaking changes into small steps.

2. Step 2: Compare options

   Options B, C, and D involve big changes or skipping testing, which increase risk.

3. Final Answer:

   To move functionality step-by-step to reduce risk -> Option D

4. Quick Check:

   Incremental migration = step-by-step safe moves [OK]

Hint: Think small safe steps, not big risky jumps [OK]

Common Mistakes:

• Assuming migration happens all at once
• Ignoring the need for testing
• Believing old services must be removed immediately

2. Which of the following is a correct step in an incremental migration plan?

easy

A. Deploy all new microservices simultaneously without routing changes

B. Use feature flags or routing to direct some traffic to new services

C. Stop the old system before starting migration

D. Skip monitoring during migration to save resources

Solution

1. Step 1: Identify safe deployment practices

   Using feature flags or routing allows gradual traffic shift to new services safely.

2. Step 2: Eliminate unsafe options

   Deploying all at once, stopping old system early, or skipping monitoring are risky.

3. Final Answer:

   Use feature flags or routing to direct some traffic to new services -> Option B

4. Quick Check:

   Routing traffic gradually = safe migration [OK]

Hint: Use routing or flags to control traffic flow [OK]

Common Mistakes:

• Deploying everything at once
• Stopping old system too early
• Ignoring monitoring during migration

3. Consider this migration step code snippet for routing traffic:

if (user.isBetaTester) {
  routeToNewService();
} else {
  routeToOldService();
}

What will happen if a user is not a beta tester?

medium

A. User traffic is dropped

B. User traffic goes to the new service

C. User traffic goes to the old service

D. User traffic causes an error

Solution

1. Step 1: Analyze the condition

   If user.isBetaTester is false, the else branch runs.

2. Step 2: Determine routing for else branch

   The else branch calls routeToOldService(), so traffic goes to old service.

3. Final Answer:

   User traffic goes to the old service -> Option C

4. Quick Check:

   Non-beta users = old service routing [OK]

Hint: False condition triggers else branch routing [OK]

Common Mistakes:

• Assuming all users go to new service
• Thinking traffic is dropped or errors occur
• Ignoring the else branch logic

4. A team started migrating a service incrementally but suddenly disabled monitoring. What is the likely problem?

medium

A. They lose visibility into errors and performance

B. They can detect issues faster

C. Migration speed increases without risks

D. Old services automatically update

Solution

1. Step 1: Understand monitoring role

   Monitoring helps detect errors and performance issues during migration.

2. Step 2: Assess impact of disabling monitoring

   Without monitoring, the team loses visibility into problems, increasing risk.

3. Final Answer:

   They lose visibility into errors and performance -> Option A

4. Quick Check:

   No monitoring = no error visibility [OK]

Hint: Never disable monitoring during migration [OK]

Common Mistakes:

• Assuming disabling monitoring improves speed
• Thinking old services update automatically
• Believing issues are easier to detect without monitoring

5. You plan to migrate a monolith to microservices incrementally. Which approach best ensures minimal downtime and rollback capability?

hard

A. Deploy new microservices behind a feature flag and route a small % of traffic gradually

B. Replace the monolith entirely in one deployment window

C. Migrate database schema all at once without backward compatibility

D. Disable old services immediately after deploying new ones

Solution

1. Step 1: Evaluate migration strategies

   Deploying behind feature flags and routing small traffic allows gradual testing and rollback.

2. Step 2: Compare risks of other options

   Replacing all at once or disabling old services causes downtime; schema changes without compatibility break systems.

3. Final Answer:

   Deploy new microservices behind a feature flag and route a small % of traffic gradually -> Option A

4. Quick Check:

   Feature flags + gradual traffic = safe migration [OK]

Hint: Use feature flags and gradual traffic shift for safety [OK]

Common Mistakes:

• Trying big-bang replacement causing downtime
• Ignoring backward compatibility in database changes
• Disabling old services too early