CSI RESTful API & Middleware Design 2

Question 1

Which HTTP status code should a REST API return when a client submits a request with a malformed JSON body?

Accepted Answer

400 Bad Request

Answer

400 Bad Request is returned when the server cannot parse the request due to malformed syntax, including invalid JSON.

Question 2

In REST API design, what is the purpose of the ETag response header?

Accepted Answer

To provide a version identifier for cache validation

Answer

ETag provides a hash or version token that clients send in If-None-Match headers to enable conditional requests and cache revalidation.

Question 3

A middleware component in an API gateway intercepts all inbound requests. Which design pattern does this exemplify?

Accepted Answer

Chain of Responsibility pattern

Answer

Chain of Responsibility passes requests along a chain of handlers (middleware), where each can process or forward the request.

Question 4

When designing a REST API for paginated collections, which approach best aligns with REST constraints?

Accepted Answer

Include pagination metadata in response headers like Link

Answer

Using Link headers (RFC 5988) keeps pagination controls hypermedia-driven and stateless, consistent with REST principles.

Question 5

Which HTTP method is idempotent but NOT safe according to REST semantics?

Accepted Answer

PUT

Answer

PUT is idempotent (multiple identical calls produce the same result) but not safe because it modifies server state.

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