Not if you don't start at zero, and no one knows where you started. Heck, add a multiplier for use in URL's even. It's not hard to come up with reversible obfuscation functions that would hide your number of users for 99.99% of cases. If you have a competitor that set on knowing your count of whatever objects then maybe you have a case. But let's say this is number of posts, clearly viewable on the website anyways. Who cares? If that sort of info is exploitable, you have to have much bigger security holes present.

> Not if you don't start at zero, and no one knows where you started.

Yes, in fact - even then. There are fascinating historical stories about lay-people who scoffed and then failed to account for the dark art of statistics. https://www.statisticshowto.datasciencecentral.com/german-ta...

At the point where you're doing all of that obfuscation, wouldn't it be easier and safer to use something like a uuid?

Use an encoded time prefix and a random part to create your UUID. I've been using such UUIDs as primary keys in Postgresql for years and I can't tell the difference in performance with say 64-bit numbers. If you don't need millions of records, even a 64-bit number with timestamp and random part will do – like "Twitter snowflake" ids.

Postgres doesn't have issues with UUIDs as primary keys; they don't need to be sorted (hash indexes were dicey before Postgres 10 but are just fine today) and Postgres doesn't row-cluster by default.

What performance cost there is (and in my experience it is not much) is because a UUID is twice as large as a bigint. And there are situations where that matters. But not that many of them.

Hash indexes can't be used for primary keys:

   postgres[7878][1]=# SELECT amname, pg_indexam_has_property(oid, 'can_unique') FROM pg_am WHERE amtype = 'i';
   ┌────────┬─────────────────────────┐
   │ amname │ pg_indexam_has_property │
   ├────────┼─────────────────────────┤
   │ btree  │ t                       │
   │ hash   │ f                       │
   │ gist   │ f                       │
   │ gin    │ f                       │
   │ spgist │ f                       │
   │ brin   │ f                       │
   └────────┴─────────────────────────┘
   (6 rows)

And postgres' btree indexes definitely are affected by the randomness in many UUID generation schemes.

Huh, so it is. And looking at our schema, it looks like the UUID/hash tables we've got don't use pkeys at all.

Looks like I have a conversation to have. Thanks. :)

Why shouldn’t you use a uuid as a primary key on most databases?

I once scraped a representative slice of Slashdot comments a while back and noticed some odd changes in their UIDs. They were originally sequential and then they switched to even numbers for a while, then odd numbers. I don't know if they were doing it to juice the UID stats to look like more people were joining the platform.

> They were originally sequential and then they switched to even numbers for a while, then odd numbers.

That sounds like they wanted to migrate to another cluster, and wanted to have both clusters running at the same time (for testing) without risking an ID overlap, so they turned the least significant bit of the ID into a cluster identifier. The older cluster was 0 (even numbers), the new cluster was 1 (odd numbers).