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200-901 Practice Question: In a microservices architecture, a REST API must…
In a microservices architecture, a REST API must support idempotent updates. Which HTTP method and design practice should be used?
⚠ Common exam trap
Cisco often tests the distinction between PUT (idempotent, full replacement) and PATCH (non-idempotent, partial update), tempting candidates to choose PATCH with conditional headers because it seems safer, but the question explicitly requires idempotent updates, which only PUT guarantees natively.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PUT with the full resource representation
PUT is inherently idempotent per HTTP/1.1 RFC 7231, meaning repeated identical requests produce the same server state. In microservices, using PUT with the full resource representation ensures that any number of identical PUT requests result in the same resource state, which is critical for safe retries in distributed systems. This aligns with RESTful design principles where PUT replaces the entire resource at the given URI.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
PUT with the full resource representation
Why this is correct
PUT is idempotent by definition; replacing the entire resource ensures the same result regardless of request count.
- ✗
POST with a unique transaction ID
Why it's wrong here
POST is not inherently idempotent; using a transaction ID can make it idempotent but adds complexity and is not a standard REST practice.
- ✗
DELETE with a resource version
Why it's wrong here
DELETE is idempotent but is used for deletion, not updates.
- ✗
PATCH with a conditional header
Why it's wrong here
PATCH can be idempotent with conditional headers, but the method itself is not guaranteed idempotent; it is not the standard approach.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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