Correlation IDs in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of Correlation IDs in Microservices

What is the main purpose of using correlation IDs in a microservices architecture?

A To uniquely identify and trace a request as it travels through multiple microservices.

B To encrypt data between microservices for security purposes.

C To balance the load evenly across all microservices instances.

D To store user session data centrally for all microservices.

💡 Hint

Think about how you can follow a single request across different services.

Correlation IDs help track a single request across multiple microservices, making debugging and monitoring easier.

❓ Architecture

intermediate

Where to Generate Correlation IDs

In a microservices system, where is the best place to generate a correlation ID for a client request?

A At the client side before sending the request.

B At every microservice independently when processing the request.

C Only in the database when storing the request data.

D At the first entry point or API gateway that receives the client request.

💡 Hint

Consider where the request first enters the system.

Generating the correlation ID at the first entry point ensures all downstream services use the same ID for tracing.

❓ scaling

advanced

Handling Correlation IDs in Asynchronous Messaging

How should correlation IDs be handled when microservices communicate asynchronously via message queues?

A Include the correlation ID in the message headers so the receiving service can continue tracing.

B Generate a new correlation ID for each message to avoid confusion.

C Do not use correlation IDs in asynchronous communication as they are only for HTTP requests.

D Store correlation IDs only in the database and not in messages.

💡 Hint

Think about how tracing continues across asynchronous boundaries.

Passing correlation IDs in message headers allows tracing across asynchronous calls just like synchronous ones.

❓ tradeoff

advanced

Tradeoffs of Using Correlation IDs in Logs

What is a potential tradeoff when including correlation IDs in every log entry across microservices?

A Including correlation IDs slows down the network communication between services.

B Correlation IDs cause security vulnerabilities by exposing sensitive data.

C Logs become larger and may increase storage and processing costs.

D Correlation IDs make logs unreadable and useless for debugging.

💡 Hint

Consider the impact on log size and storage.

Adding correlation IDs to logs increases log size, which can raise storage and processing costs, but improves traceability.

❓ estimation

expert

Estimating Correlation ID Storage Impact

A microservices system processes 1 million requests per hour. Each request generates logs in 5 services, each log entry includes a 36-character UUID correlation ID. Estimate the additional storage needed per hour just for storing correlation IDs in logs, assuming each log entry stores only the correlation ID as a string (1 character = 1 byte).

A Approximately 36 MB per hour

B Approximately 180 MB per hour

C Approximately 720 MB per hour

D Approximately 5 MB per hour

💡 Hint

Calculate total log entries and multiply by correlation ID size in bytes.

1 million requests × 5 logs = 5 million entries. Each entry 36 bytes. Total = 5,000,000 × 36 = 180,000,000 bytes ≈ 180 MB.