❄️ SnowID Rust

May 23, 2026 · View on GitHub

Crates.io Documentation License: MIT

A Rust implementation of a Snowflake-like ID generator with 42-bit timestamp.

Generate 64-bit unique identifiers that are:

  • ⚡️ Fast (~22ns per ID with default logical generation, ~722-841ns for 1,024-ID batches)
  • 📈 Time-sorted
  • 🔄 Monotonic
  • 🔒 Thread-safe
  • 🌐 Distributed-ready
  • 🎯 Minimal dependencies (base62 for encoding)

🧮 ID Structure

Example ID: 151819733950271234

Default configuration:

|------------------------------------------|------------|------------|
|           TIMESTAMP (42 bits)            | NODE (10)  |  SEQ (12)  |
|------------------------------------------|------------|------------|
  • Timestamp: 42 bits = 139 years from 2024-01-01 (1704067200000)
  • Node ID: 10 bits = 1,024 nodes (valid range: 6-16 bits)
  • Sequence: 12 bits = 4,096 IDs/ms/node

🎯 Quick Start

[dependencies]
snowid = "3.0.0"

use snowid::SnowID;

fn main() {
    let gen = SnowID::new(1).unwrap();
    let id = gen.generate();
    println!("Generated ID: {}", id);
}

generate() uses logical timestamp generation by default: it always returns an ID and advances the timestamp component instead of waiting when the current millisecond's sequence range is exhausted.

🔠 Base62 Encoded IDs

Generate base62 encoded IDs (using characters 0-9, a-z, A-Z) for more compact and URL-friendly identifiers:

use snowid::SnowID;

fn main() {
    // Create a generator
    let gen = SnowID::new(1).unwrap();

    // Generate a base62 encoded ID
    let encoded_id = gen.generate_base62();
    println!("Base62 ID: {}", encoded_id); // Example: "2qPfVQh7Jw9"

    // Generate with raw value
    let (encoded_id, raw_id) = gen.generate_base62_with_raw();
    println!("Base62: {}, Raw: {}", encoded_id, raw_id);

    // Decode a base62 ID back to u64
    let decoded = gen.decode_base62(&encoded_id).unwrap();
    assert_eq!(decoded, raw_id);

    // Extract components from a base62 ID
    let (timestamp, node, sequence) = gen.decompose_base62(&encoded_id).unwrap();
    println!("Timestamp: {}, Node: {}, Sequence: {}", timestamp, node, sequence);
}

Benefits of Base62 IDs

  • 🔤 More compact representation (11 chars max vs 20 digits for u64)
  • 🔗 URL-friendly (no special characters)
  • 👁️ Human-readable and easier to share
  • 🔄 Directly encodes the same 64-bit SnowID value

🔧 Configuration

use snowid::{SnowID, SnowIDConfig};

fn main() {
    // Create custom configuration
    let config = SnowIDConfig::builder()
        .epoch(1577836800000) // 2020-01-01 00:00:00 UTC
        .node_bits(8).unwrap()         // Supports 255 nodes
        .build();

    // Create generator with custom config
    let gen = SnowID::with_config(1, config).unwrap();
}

Epochs are validated when creating a generator. SnowID rejects epochs in the future and epochs old enough that the 42-bit timestamp field cannot represent the current time, preventing silent timestamp wrap or duplicate ID collisions.

ℹ️ Available Methods

use snowid::{SnowID, base62};

fn main() {
    let gen = SnowID::new(1).unwrap();

    // Generate numeric IDs
    let id = gen.generate();  // Default logical mode: never waits; timestamp can run ahead under overload
    let maybe_id = gen.try_generate();  // Non-blocking: returns Err when current millisecond is exhausted

    // Reserve many IDs with one atomic update for throughput-oriented hot paths
    let mut batch = [0u64; 128];
    gen.generate_batch(&mut batch);  // Always fills; timestamp can run ahead under overload
    let written = gen.try_generate_batch(&mut batch);  // May return fewer than batch.len() without waiting

    // Generate Base62 encoded IDs (allocates String)
    let base62_id = gen.generate_base62();
    let (base62_id, raw_id) = gen.generate_base62_with_raw();

    // Zero-allocation Base62 generation (for hot paths)
    let (bytes, len) = gen.generate_base62_array();  // Returns [u8; 11] + length
    let mut buf = [0u8; base62::MAX_LEN];
    let (str_ref, raw_id) = gen.generate_base62_into(&mut buf);  // Returns &str + raw ID

    // Decode Base62 IDs
    let decoded = gen.decode_base62(&base62_id).unwrap();
    let (ts, node, seq) = gen.decompose_base62(&base62_id).unwrap();

    // Extract individual components from numeric IDs
    let timestamp = gen.extract.timestamp(id);  // Get timestamp from ID
    let node = gen.extract.node(id);           // Get node ID from ID
    let sequence = gen.extract.sequence(id);    // Get sequence from ID

    // Extract all components at once
    let (ts, node, seq) = gen.extract.decompose(id);

    // Configuration information
    let max_node = gen.config.max_node_id();          // Get maximum allowed node ID
    let node_bits = gen.config.node_bits();           // Get number of bits used for node ID
    let max_seq = gen.config.max_sequence_id();    // Get maximum sequence per millisecond
    let timestamp_bits = SnowID::TIMESTAMP_BITS; // Get number of bits used for timestamp (42)
}

⏳ Logical Overflow Handling

Default generate() does not wait on per-millisecond sequence exhaustion; it advances a logical timestamp and returns immediately. IDs stay unique and monotonic for the generator, but the timestamp component can run ahead of wall-clock time during sustained overload.

For callers that must never advance logical time, use try_generate(). It returns immediately with an error when the current millisecond has exhausted its sequence values or when the generator's logical timestamp is ahead of wall-clock. For burst-heavy workloads, use try_generate_batch(&mut [u64]); it reserves a contiguous sequence range with one atomic state update and returns the number of IDs written without waiting for the next millisecond.

📊 Performance & Comparisons

Social Media Platform Configurations

PlatformTimestampNode BitsSequence BitsMax NodesIDs/ms/node before logical rolloverDefault generate() Time/ID
Twitter4110121,0244,096~22ns
Instagram4113108,1921,024~22ns
Discord4210121,0244,096~22ns

Node vs Sequence Bits Trade-off

Node BitsMax NodesIDs/ms/node before logical rolloverDefault generate() Time/ID
66465,536~22ns
825616,384~22ns
101,0244,096~22ns
124,0961,024~22ns
1416,384256~22ns
1665,53664~24ns

Choose configuration based on your needs:

  • More nodes → Increase node bits (max 16 bits = 65,536 nodes)
  • More IDs per node → Increase sequence bits (min 6 node bits = 64 nodes)
  • Total bits (node + sequence) is fixed at 22 bits

For default logical generation, node_bits controls how many IDs fit in a real millisecond before the generator rolls forward to a logical timestamp. It no longer forces the hot path to wait. On a local Apple Silicon benchmark run (cargo bench --bench perf_hotspots -- "Hotspot Generate Capacity/node_bits/<N>"), node_bits=6, node_bits=10, and node_bits=16 all measured around ~22ns per ID. Use try_generate() when callers prefer an immediate non-blocking failure over logical timestamp advancement.

Shared-generator contention is the other major throughput factor. A single shared generator is lock-free, but all threads still update one atomic state. In the same local benchmark run, 8 threads sharing one generator for 1,024 IDs each took about 2.64ms, while 8 per-thread generators took about 145µs. If your topology allows it, prefer one generator per thread, worker, or shard with distinct node IDs for peak throughput.

For burst generation, generate_batch(&mut [u64]) reserves a logical timestamp range with one atomic update and fills the whole buffer. try_generate_batch(&mut [u64]) is available when callers prefer partial non-blocking reservation. On the same machine, filling 1,024 IDs with generate_batch() took about 721.62-840.74ns, while calling generate() 1,024 times took about 24.25µs. That is roughly a 32x throughput improvement for callers that can consume IDs in batches.

Focused hotspot benchmarks are available for validating your target machine without running the full benchmark suite:

cargo bench --bench perf_hotspots -- "Hotspot Generate Capacity/node_bits/10"
cargo bench --bench perf_hotspots -- "Hotspot Logical Generation/generate/node_bits/16/batch/1024"
cargo bench --bench perf_hotspots -- "Hotspot Batch Reservation/generate_batch/1024"
cargo bench --bench perf_hotspots -- "Hotspot Batch Reservation/try_generate_batch/1024"
cargo bench --bench perf_hotspots -- "Hotspot Batch Reservation/generate_loop/1024"
cargo bench --bench perf_hotspots -- "Hotspot Shared Generator/threads/8/ops_per_thread/1024"
cargo bench --bench perf_hotspots -- "Hotspot Per Thread Generator/threads/8/ops_per_thread/1024"

Int64 vs Base62 Performance

VariantTime/IDSizeNotes
Int64~22 ns18-20 digitsFastest single-ID option
Base62 (String)~40 ns10-11 charsCompact, URL-friendly
Base62 (array)~24 ns10-11 charsZero-allocation, hot paths
Base62 (into)~24 ns10-11 charsZero-allocation, reuse buffer

These Base62 numbers include ID generation plus encoding from the targeted ID Generation Comparison benchmark.

Base62 encoding provides more compact, URL-friendly IDs. For hot paths, use generate_base62_array() or generate_base62_into() to avoid heap allocations.

🚀 Examples

Check out examples for:

  • Basic usage
  • Custom configuration
  • Base62 encoding and decoding
  • Performance comparisons between Int64 and Base62
  • Distributed generation
  • Performance benchmarks

🧪 Correctness Stress Testing

The test suite includes deterministic unit tests, high-load multithread tests, and property-based tests for ID uniqueness, monotonicity, sequence bounds, logical timestamp rollover, and batch generation. For Stryker-style mutation testing in Rust, see MUTATION_TESTING.md for cargo-mutants commands and release-gate guidance.

📜 License

MIT - See LICENSE for details