Event store concept in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of an event store in microservices?

In a microservices architecture, what is the main role of an event store?

A To act as a cache layer for frequently accessed data.

B To store only the current state of each microservice for quick access.

C To store all changes to application state as a sequence of events.

D To manage user authentication and authorization events.

💡 Hint

Think about how event sourcing captures changes over time.

An event store records every change as an event, preserving the full history of state changes. This allows rebuilding state and auditing.

❓ Architecture

intermediate

Which component typically reads from the event store to update read models?

In an event-driven microservices system, which component consumes events from the event store to update the read database?

A Event projector

B Command handler

C API gateway

D Service registry

💡 Hint

Consider the component responsible for transforming events into queryable data.

The event projector listens to events and updates read models to provide efficient query access.

❓ scaling

advanced

How to scale an event store to handle high write throughput?

You have a microservices system with an event store that receives thousands of events per second. Which approach best helps scale the event store for high write throughput?

A Batch all events into a single large transaction every hour.

B Use a single centralized database with strong consistency for all events.

C Store events only in memory to speed up writes.

D Partition the event store by aggregate ID to distribute writes across nodes.

💡 Hint

Think about distributing load to avoid bottlenecks.

Partitioning by aggregate ID allows parallel writes to different partitions, improving throughput and scalability.

❓ tradeoff

advanced

What is a tradeoff of using an event store for state management?

Using an event store to manage application state has benefits but also tradeoffs. Which of the following is a common tradeoff?

A Event stores require more storage space due to storing all events.

B Event stores eliminate the need for any read models.

C Event stores simplify debugging by hiding event history.

D Event stores guarantee zero latency for all queries.

💡 Hint

Consider what storing every change implies for storage.

Storing every event means the event store grows over time, requiring more storage compared to storing only current state.

❓ estimation

expert

Estimate storage needed for event store with 1 million events/month

Your microservices system generates about 1 million events per month. Each event averages 1 KB in size. Estimate the storage needed for 1 year of events, including a 20% overhead for indexing and metadata.

A Approximately 12 GB

B Approximately 14.4 GB

C Approximately 10 GB

D Approximately 8.4 GB

💡 Hint

Calculate total event size, then add 20% overhead.

1 million events/month × 12 months = 12 million events/year. Each event is 1 KB, so 12 million KB = 12 GB. Adding 20% overhead: 12 GB × 1.2 = 14.4 GB.