Microservices Resilience and Fault Tolerance Questions and Answers

Question 1

A high-traffic e-commerce application has a 'Recommendation' service that sometimes experiences high latency.
This service is called by the 'Product Details' service.
During peak load, the slow 'Recommendation' service causes all available threads in the 'Product Details' service's thread pool to become blocked, waiting for a response.
This, in turn, makes the 'Product Details' service unresponsive to all other requests, causing a cascading failure.
Which resilience pattern is specifically designed to isolate failures and prevent them from exhausting resources in this manner?

Accepted Answer

Bulkhead

Answer

Circuit Breaker

Answer

Fallback

Answer

Retry

Question 2

In a microservices architecture, what is the primary reason for configuring timeouts for synchronous calls between services?

Accepted Answer

To prevent a calling service from being blocked indefinitely, thereby releasing resources and avoiding cascading failures.

Answer

To provide a cached or default response when the downstream service is unavailable.

Answer

To automatically retry the request if the initial attempt fails.

Answer

To ensure that the calling service waits indefinitely for a response to maintain data consistency.

Question 3

When a service attempts to communicate with another service and encounters a transient failure, such as a temporary network issue, which of the following is the most effective strategy to handle the error while preventing the client from overwhelming the downstream service?

Accepted Answer

Implementing a retry mechanism with an exponential backoff and jitter.

Answer

Immediately retrying the request in a tight loop until it succeeds.

Answer

Failing fast and immediately returning an error to the user.

Answer

Implementing a retry mechanism with a fixed delay between each attempt.

Question 4

A user dashboard service aggregates data from several other microservices, including a 'UserProfile' service (critical) and a 'WeatherWidget' service (non-critical). If the 'WeatherWidget' service fails or times out, the entire dashboard fails to load, resulting in a poor user experience. To improve the resilience of the dashboard, what pattern should be implemented to handle the failure of the non-critical 'WeatherWidget' service?

Accepted Answer

A Fallback pattern to provide a default or cached response for the weather data.

Answer

An aggressive Retry pattern to continuously attempt to contact the 'WeatherWidget' service.

Answer

A Bulkhead pattern to isolate the 'WeatherWidget' call into its own thread pool.

Answer

A Saga pattern to ensure the transaction is eventually consistent.

Question 5

What is the primary purpose of implementing a `/health` or `/healthz` API endpoint in a microservice?

Accepted Answer

To allow a container orchestrator or load balancer to determine if the service instance is running and able to handle requests.

Answer

To expose a public endpoint for end-users to check the overall status of the application.

Answer

To provide detailed application performance metrics and logs to a monitoring system.

Answer

To trigger a manual restart of the service if it becomes unresponsive.

Question 6

A 'Shipping' service needs to call an external 'AddressValidation' service, which is known to be occasionally slow or unreliable. To ensure the 'Shipping' service remains stable and responsive, the development team wants to implement a comprehensive resilience strategy. Which combination of patterns provides the most robust fault tolerance for this scenario?

Accepted Answer

Circuit Breaker, Retry with Exponential Backoff, and a Timeout.

Answer

A single, long Timeout to wait for the unreliable service to respond.

Answer

Event Sourcing and Command Query Responsibility Segregation (CQRS).

Answer

API Gateway Aggregation and Service Discovery only.