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DevOps & Automation · Foundational

Idempotency

The property that applying the same operation multiple times produces the same result as applying it once.

Definition

Idempotency is central to configuration management, IaC, and APIs: rerunning a playbook or terraform apply should make no further changes once the desired state is reached. In REST, GET, PUT, and DELETE are idempotent while POST is not.

Example

Running an Ansible task with state: present twice reports 'changed' the first time and 'ok' the second.

Exam tip

Exam questions often ask which HTTP method is not idempotent (POST) or why idempotent modules beat raw shell commands.

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