What is Idempotent?

The term idempotent has a specific meaning depending on the context, but the core idea is the same:
an operation is idempotent if performing it multiple times has the same effect as performing it once.

In Programming

An operation (e.g. a function or method) is idempotent if calling it multiple times with the same input
always produces the same result and has the same side effects as calling it once.

Example in HTTP:

• GET is idempotent: Getting a resource multiple times doesn’t change it.
• PUT is idempotent: Updating a resource with the same data multiple times has the same effect as updating it once.
• POST is not idempotent: Submitting the same data multiple times might create multiple records.

In Mathematics

A function f is idempotent if applying it more than once does not change the result:

f(f(x)) = f(x)
  

Example:

Let f(x) = |x| (absolute value). Then:

f(f(-3)) = f(3) = 3 = f(-3)
  

So it’s idempotent.

Let me know if you’re thinking of idempotency in a specific area like APIs, databases, or functional programming—I can tailor the explanation!