Random identifiers can be bad for performance when inserting into balanced b-tree indexes.
| variant | timestamp bits | random bits |
| -------------- | ---------------------------------------- | ----------- |
| u32, i32 | 16 (hours since unix epoch) | 16 |
| u64, i64 | 40 (seconds since unix epoch) | 24 |
| u128, i128 | 64 (milliseconds since unix epoch) | 64 |