Parallel running in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is parallel running in system design?

Parallel running is a method where two systems operate simultaneously to compare results and ensure the new system works correctly before fully replacing the old one.

beginner

Why is parallel running important in microservices migration?

It helps verify that the new microservices behave as expected without disrupting the existing system, reducing risk during transition.

intermediate

Name a key challenge when implementing parallel running.

Synchronizing data and requests between old and new systems to ensure consistent results can be complex and resource-intensive.

intermediate

How does parallel running differ from a blue-green deployment?

Parallel running runs both systems fully and compares outputs, while blue-green switches traffic between two environments without running both fully in production.

beginner

What is a common indicator that parallel running is successful?

When outputs from both old and new systems match consistently over a period, showing the new system is reliable.

What is the main goal of parallel running?

A To replace the old system immediately

B To reduce system resources by shutting down old services

C To run two systems simultaneously to verify correctness

D To deploy only one system at a time

Parallel running involves running both old and new systems together to compare results and ensure the new system works correctly.

Which of the following is a challenge in parallel running?

A Ensuring data synchronization between systems

B Ignoring old system outputs

C Deploying only one microservice

D Running systems at different times

Synchronizing data and requests between old and new systems is a key challenge in parallel running.

Parallel running is most useful during which phase?

A Initial system design

B System migration or upgrade

C System decommissioning

D Performance tuning

Parallel running is used during migration or upgrade to validate the new system before full cutover.

How does parallel running reduce risk?

A By allowing comparison of outputs before full switch

B By immediately shutting down the old system

C By ignoring errors in the new system

D By running only the new system

It reduces risk by running both systems and comparing outputs to catch issues early.

Which deployment strategy is closest to parallel running?

A Canary deployment

B Blue-green deployment

C Rolling update

D Shadow testing

Shadow testing runs new code alongside old without affecting users, similar to parallel running's simultaneous operation.

Explain the concept of parallel running and why it is used in microservices migration.

Think about running two versions side by side to compare results.

Describe the main challenges faced when implementing parallel running in a microservices environment.

Consider what makes running two systems at once difficult.