Easy Explanation of HTTP Idempotent Requests

When making a RESTful API, we often use POST, PUT, and PATCH. Let's look at the differences between them and also find out which HTTP method is idempotent.

POST (Create)

• Idempotency: POST is not idempotent.

• Goal: This HTTP method is mainly used for creating new resources (records).

• Example: When you use POST to create a new resource, each request with the same payload will typically result in a new resource being created. This could lead to duplicate entries if the server does not handle duplicates. For instance, if you send a POST request to create a new user with the same details multiple times, you might end up with multiple user records.

PUT (Update/Replace/Create)

• Idempotency: PUT is idempotent.

• Goal: It is mainly used to update or replace existing records. If a record doesn't exist, it can create one.

• Example: When you making the same request multiple times will have the same effect as making it once. If you use PUT to update a user profile, sending the same request again will not change the outcome after the first request. If the resource does not exist, PUT can create it, and subsequent identical requests will simply ensure the resource is in the desired state.

PATCH (Partial Update)

• Idempotency: PATCH is not idempotent by nature, but it can be made idempotent under certain conditions.

• Goal: This HTTP method is mainly used for partially updating existing resources (records), modifying only specific fields or attributes rather than the entire record.

• Example: PATCH is used for partial updates. While PATCH is not inherently idempotent, it can be idempotent if designed that way. For example, if you send a PATCH request to update only the email field of a user profile, repeating the request with the same data will result in the same outcome, as only the specified field is modified.

Choosing the right HTTP method helps developers make their APIs efficient, predictable, and in line with RESTful principles. Knowing about idempotency helps manage resource states and prevents unexpected changes in API interactions.

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