What is idempotency?

Idempotence is a property of an operation where performing it multiple times yields the same result as performing it once.

In simpler terms, if you call a function or execute a request multiple times in a row, the state of the system does not change after the first call.

An example of an idempotent operation is setting a variable's value:

x = 5
x = 5  # repeated assignment will not change the value

In web development, HTTP methods GET, PUT, DELETE are considered idempotent because repeated requests do not further change the server's state.

In the context of databases, for example, updating a record with the same value is idempotent, but adding a new record is not, as repeated additions can create duplicates.

Idempotence is important for system reliability, especially when dealing with repeated requests due to network failures or errors.