Microservice communication basics in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding synchronous vs asynchronous communication

Which statement correctly describes the difference between synchronous and asynchronous communication in microservices?

A Synchronous communication waits for a response before continuing, while asynchronous communication does not wait and proceeds immediately.

B Synchronous communication never waits for a response, asynchronous always waits for a response.

C Asynchronous communication requires both services to be online at the same time, synchronous does not.

D Synchronous communication uses message queues, asynchronous uses direct HTTP calls.

💡 Hint

Think about whether the sender waits for the receiver to reply before moving on.

Synchronous communication means the sender waits for the receiver's response before continuing. Asynchronous communication allows the sender to continue without waiting.

❓ Architecture

intermediate

Choosing communication method for microservices

You have two microservices: one handles user authentication and the other processes payments. Which communication method is best when the payment service must confirm user identity before processing?

A Use synchronous HTTP calls so the payment service waits for authentication response before proceeding.

B Use asynchronous messaging with a message queue to send user identity and wait for confirmation.

C Use asynchronous event broadcasting without waiting for any response.

D Use direct database access by the payment service to check user identity.

💡 Hint

Consider if the payment service needs immediate confirmation before continuing.

Synchronous HTTP calls are best when the payment service must wait for user authentication confirmation before processing payments.

❓ scaling

advanced

Scaling microservices with asynchronous communication

Which benefit does asynchronous communication provide when scaling microservices?

A It requires all services to be tightly coupled, improving coordination.

B It forces all services to process requests in a strict order, reducing complexity.

C It allows services to handle requests independently without waiting, improving throughput and resilience.

D It eliminates the need for message brokers or queues.

💡 Hint

Think about how asynchronous communication affects service independence and load handling.

Asynchronous communication lets services work independently and not wait for each other, which helps handle more requests and recover from failures.

❓ tradeoff

advanced

Tradeoffs of using message queues in microservices

What is a common tradeoff when using message queues for microservice communication?

A Guaranteed real-time responses but no fault tolerance.

B Improved decoupling and reliability but increased complexity and potential message delays.

C No need for service discovery but requires synchronous calls.

D Simpler architecture but no support for retrying failed messages.

💡 Hint

Consider what message queues add and what challenges they introduce.

Message queues help decouple services and improve reliability but add complexity and can cause delays due to asynchronous processing.

❓ estimation

expert

Estimating message queue capacity for microservices

You expect 10,000 requests per minute between two microservices communicating asynchronously via a message queue. Each message is about 1 KB. What is the minimum required throughput of the message queue in MB per second?

A Approximately 1.67 MB/s

B Approximately 0.017 MB/s

C Approximately 16.7 MB/s

D Approximately 0.17 MB/s

💡 Hint

Calculate total KB per minute, convert to MB, then divide by 60 seconds.

10,000 messages/min × 1 KB = 10,000 KB/min = 10 MB/min. 10 MB ÷ 60 sec ≈ 0.167 MB/s.