Demo vs Reality

For those of you who’ve shipped infrastructure or automation systems into real workflows:

what kind of gap do you usually see between demo/stress test results and real-world behavior once users start interacting with it adversarially or unpredictably?

Roughly speaking:

How much of what “passed” in controlled testing later broke in production?

Was it 5–10% edge cases?

20–30%?

Or did entirely new classes of failure appear?

We’re at the stage where our system behaves deterministically under synthetic chaos (retries, races, crashes), and I’m trying to sanity-check expectations before wider exposure.

Would love to hear concrete war stories rather than theory