200-901 Understanding and Using APIs Practice Question
A developer is designing a Python script that interacts with a REST API. The script must handle common HTTP methods appropriately. Which TWO of the following statements correctly describe the use of HTTP methods in RESTful APIs? (Choose two.)
⚠ Common exam trap
The trap here is assuming that all methods that modify state are non-idempotent, or that DELETE is not idempotent because it might return an error on subsequent calls.
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
✓
GET requests should be idempotent and safe, meaning they do not modify server state.
In REST, GET is safe and idempotent, and PUT is idempotent and used for full updates or replacements. POST is neither safe nor idempotent, DELETE is idempotent despite possible error responses, and PATCH is not guaranteed to be idempotent or safe. Understanding these properties helps developers choose the correct method and handle retries appropriately.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
GET requests should be idempotent and safe, meaning they do not modify server state.
Why this is correct
In REST, GET is defined as a safe and idempotent method. Safe means it does not alter server state, and idempotent means multiple identical requests have the same effect as a single one. This is why GET is used for retrieving data without side effects, and clients can cache or retry GET requests without concern for unintended changes.
- ✗
POST requests are idempotent, so sending the same POST request multiple times has the same effect as sending it once.
Why it's wrong here
POST is not idempotent. Sending the same POST request multiple times typically creates multiple resources or triggers multiple actions, each with its own effect. For example, submitting an order form twice could result in two orders. This is why POST is used for operations that are not safe to repeat without additional safeguards like idempotency keys.
- ✗
PATCH requests must always be idempotent and safe.
Why it's wrong here
PATCH is not necessarily idempotent or safe. It is used for partial updates, and depending on the operation, repeating the same PATCH might produce different results. For example, a PATCH that increments a counter is not idempotent. PATCH also modifies server state, so it is not safe. Therefore, this statement is incorrect.
- ✓
PUT requests are idempotent and are used to update or replace a resource entirely.
Why this is correct
PUT is idempotent because sending the same request multiple times results in the same state on the server. It is used to update or replace a resource at a known URI. If the resource does not exist, PUT may create it. Because it replaces the entire resource, repeated PUTs with the same data yield the same outcome.
- ✗
DELETE requests are not idempotent because deleting a resource twice will cause an error the second time.
Why it's wrong here
DELETE is idempotent. Although the second DELETE might return a 404 Not Found, the state of the server after the first DELETE is unchanged by the second attempt. Idempotency refers to the effect on the server state, not the response status. So DELETE is considered idempotent even if subsequent calls return errors.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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