Method semantics tell clients how operations should behave. Safe methods should not request state changes; idempotent operations have the same intended effect when repeated.
Before you start
You should understand clients, servers, IP addresses and ports. Follow a request through name resolution, connection establishment and application exchange. Distinguish protocol guarantees from deployment policy, and use observations from the relevant layer rather than guessing from one browser error message.
The practical goal is to reason through this situation: PUT can replace one resource repeatedly, while POST may create new operations. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Separate safety and repetition
Safe concerns requested state changes; idempotent concerns repeated intended effects.
Step 2: Read actual operation meaning
A method name alone cannot guarantee a correctly implemented contract.
Step 3: Choose retry policy
Uncertain mutations need stable identity or outcome reconciliation.
Worked scenario
PUT can replace one resource repeatedly, while POST may create new operations.
Repeated PUT replacing one resource can have the same intended stored result even if responses or audit logs differ. Repeated POST creating orders may create several orders unless the server implements idempotency. GET that triggers a purchase violates safe semantics and can be activated by ordinary link-handling behavior.
Common mistake
Idempotence does not mean identical responses or no logging side effects.
Verify the behavior
Repeat requests and inspect business state, not only identical response text.
Interview exercise
Choose a retry policy.
Answer and reasoning
Consider method semantics and the actual server contract, using operation identity for mutations whose outcome can be uncertain.
Continue learning
Compare the scenario with the Networking interview questions and test your understanding with the Networking MCQs. For terminology and implementation details, consult the reference material.