Quick Answer
The answer is API Gateway, Circuit Breaker, and Service Registry. The API Gateway pattern acts as a single entry point for all client requests, routing them to appropriate microservices while handling cross-cutting concerns like authentication and rate limiting. The Circuit Breaker pattern prevents cascading failures by monitoring service calls and opening a circuit to stop requests when a failure threshold is reached, allowing the failing service time to recover—a concept tested heavily in the Cisco DevNet Associate 200-901 exam under resilience and fault tolerance. The Service Registry pattern enables dynamic service discovery, where microservices register their network locations so clients can find them without hardcoded addresses. On the exam, a common trap is confusing the Service Mesh pattern with API Gateway, but remember: the gateway is the front door, the registry is the phone book, and the circuit breaker is the fuse box. A useful memory tip is "GRC" for Gateway, Registry, Circuit breaker.
This 200-901 practice question tests your understanding of software development and design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which THREE of the following are common design patterns for microservices? (Choose three.)
Chain of Responsibility
Why wrong: Incorrect: This is a behavioral pattern, not specific to microservices.
Circuit Breaker
Correct: Circuit Breaker is used for fault tolerance.
Singleton
Why wrong: Incorrect: Singleton is a general OOP pattern.
Service Registry
Correct: Service Registry is used for service discovery.
API Gateway
Correct: API Gateway is a common microservices pattern.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Circuit Breaker
The Circuit Breaker pattern (B) is a common microservices design pattern that prevents cascading failures by monitoring for failures and opening a circuit to stop requests to a failing service, allowing it to recover. It is widely implemented in frameworks like Netflix Hystrix or Resilience4j, where states (closed, open, half-open) control request flow and timeout thresholds.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Chain of Responsibility
Why it's wrong here
Incorrect: This is a behavioral pattern, not specific to microservices.
Circuit Breaker
Why this is correct
Correct: Circuit Breaker is used for fault tolerance.
Related concept
Read the scenario before looking for a memorised answer.
Singleton
Why it's wrong here
Incorrect: Singleton is a general OOP pattern.
Service Registry
Why this is correct
Correct: Service Registry is used for service discovery.
Related concept
Read the scenario before looking for a memorised answer.
API Gateway
Why this is correct
Correct: API Gateway is a common microservices pattern.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the distinction between general software design patterns (like Singleton or Chain of Responsibility) and patterns specifically designed for microservices architecture, such as Circuit Breaker, Service Registry, and API Gateway.
Detailed technical explanation
The Circuit Breaker pattern works by tracking recent failures (e.g., 5 failures in a 10-second window) to trip the circuit from closed to open, then after a configurable timeout (e.g., 30 seconds), it transitions to half-open to test if the service has recovered. In real-world scenarios, this prevents thread pool exhaustion in systems like Netflix, where a single slow dependency could otherwise block all request threads.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Software Development and Design — This question tests Software Development and Design — Read the scenario before looking for a memorised answer..
The correct answer is: Circuit Breaker — The Circuit Breaker pattern (B) is a common microservices design pattern that prevents cascading failures by monitoring for failures and opening a circuit to stop requests to a failing service, allowing it to recover. It is widely implemented in frameworks like Netflix Hystrix or Resilience4j, where states (closed, open, half-open) control request flow and timeout thresholds.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This 200-901 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-901 exam.
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