Feature itself and its practical use cases are clear. It seems like the bottom line is that when you get record locking errors with high-volume transactions involving No. Series, you should consider flipping the No. Series to Sequential and advise users that gaps may exist in the future.
On another note, i was thinking that “external facing” No. Series could be random, yet unique. This could solve not only the performance issue, but it also could address potentially fraudulent activity.
If posted invoice numbers are sequential and visible (on a customer-facing invoice, packing slip, or portal), an outsider can infer your volume and cadence "Invoice 100234 today, so you're issuing roughly 40/day." That lets a fraudster fabricate a plausible fake invoice number when impersonating a vendor or submitting a fraudulent payment request, since it won't stand out as obviously wrong to someone eyeballing it.
And this is just one example i can think of.
