🧙 Druid

Fast, time-ordered identifier generation in Rust. Druid provides both a high-entropy custom format and RFC 9562-compatible UUIDv7 bytes.

Quick start

Add the Git dependency:

[dependencies]
druid = { git = "https://github.com/GrandEngineering/druid" }

Generate, format, and parse an ID:

use druid::{Druid, DruidV7};

let id = Druid::new();
println!("{id}"); // 80 lowercase hexadecimal characters
assert_eq!(id, id.to_string().parse()?);

let uuid_v7 = DruidV7::new();
assert_eq!(uuid_v7.as_bytes().len(), 16);
# Ok::<(), druid::ParseDruidError>(())

Default::default() remains available for both types.

Formats

Druid — 40 bytes

Bytes	Contents
0..16	Big-endian Unix timestamp in nanoseconds
16..39	184 random bits from the operating system RNG
39	Format version (0)

DruidV7 — 16 bytes

DruidV7 follows the UUIDv7 byte layout from RFC 9562, including its 48-bit millisecond timestamp, version, and variant bits.

Both types implement Copy, Display, FromStr, Ord, Hash, and AsRef<[u8]>. Raw bytes are available through as_bytes() and validated by from_bytes().

Ordering and uniqueness

The timestamp prefix makes IDs naturally sortable across different clock ticks. IDs generated in the same nanosecond (Druid) or millisecond (DruidV7) use random data for the remaining order and therefore do not necessarily preserve generation order. System clock rollback can also affect ordering.

A Druid has 184 random bits per timestamp value. Using the birthday bound, approximately 7.0 × 10²⁶ IDs generated in one timestamp bucket produce a 1% collision probability. This is a probabilistic guarantee, not a substitute for a database uniqueness constraint when duplicates must be impossible.

These identifiers expose creation time and are not intended to be secrets.

Development

cargo fmt --check
cargo clippy --all-targets --all-features -- -D warnings
cargo test --all-features
cargo doc --no-deps
cargo bench

The benchmark suite compares individual and parallel batches of Druid, UUIDv7, CUID2, and UUIDv4 generation. Results depend on hardware, Rust version, and dependency versions; run it locally rather than relying on stale published numbers.

License

Licensed under GPL-3.0-only.