The example is not really great, but Idempotency is a very important concept for everything 'data'. You very much want to be able to run the same pipeline seve

The example is not really great, but Idempotency is a very important concept for everything 'data'. You very much want to be able to run the same pipeline several times and get the same result, or overwrite the results if you changed the inputs. You don't want to wonder if somewhere down the line, there will be duplicated data that will corrupt results for processes that consumes this data - you just want to be able to re-run your pipeline. Sadly, that's not how many systems seem to be designed.