I’ve been working on a robust scheme for encrypted sequential IDs, which is done, including library implementations in Rust, JavaScript and Python, pending just a smidgeon more writing about it and reviewing a decision on naming. You store an integer in the database, then encrypt it with a real block cipher, and stringify with Base58. I have three modes: one for 32-bit IDs, using Speck32/64 and producing 4–6 character IDs; one for 64-bit IDs, using Speck64/128 and producing 8–11 character IDs; and one hybrid, using the 32-bit mode for IDs below 2³² and the 64-bit mode above that, providing both a forwards-compatibility measure and a way of producing short IDs as long as possible. Contact me (see my profile) if you’re interested, or I’ll probably publish it in another day or two. Trouble is that I’ve been getting distracted with other related concepts, like optimally-short encoding by using encryption domains [0, 58¹), [58¹, 58²), …, [58¹⁰, 2⁶⁴) (this is format-preserving encryption; the main reputable and practical choices I’ve found are Hasty Pudding, which I’ve just about finished implementing but would like test vectors for but they’re on a dead FTP site, and NIST’s FF1 and FF3, which are patent-encumbered), and ways of avoiding undesirable patterns (curse words and such) by skipping integers from the database’s ID sequence if they encode to what you don’t want, and check characters with the Damm algorithm. If I didn’t keep getting distracted with these things, I’d have published a couple of weeks ago.

(I am not aware of any open-source library embodying a scheme like what I propose—all that I’ve found have either reduced scope or badly broken encryption; https://github.com/yi-jiayu/presents encrypts soundly, but doesn’t stringify; Hashids is broken almost beyond belief and should not be considered encryption; Optimus uses an extremely weak encryption.)

UUIDs are crazy overkill in any situation where you can have centralised ID allocation. Fully decentralised? Sure, 128 bits of randomness or mixed clock and randomness or similar, knock yourself out. But got a master database? Nah, you’re just generating unreasonably long values that take up unnecessary space and make for messy URLs and such.