Distributed Unique ID Generator — Notes

Requirements

• Globally unique 64-bit IDs.
• Roughly time-sortable.
• 10k+ IDs/s per node, 1M+ aggregate cluster.
• No single point of failure.

Snowflake math

• 4096 IDs/ms × 1000 ms × 1024 workers = 4.2 billion IDs/sec theoretical.
• 41-bit ms gives 2^41 / (365864001000) ≈ 69.7 years from custom epoch.

API

GET /v1/id              -> 64-bit integer
POST /v1/ids?count=100  -> batch

Operational concerns

• Worker ID assignment: ZooKeeper sequential ephemeral nodes; release on shutdown.
• Clock: chrony with hard sync; disable step (use slew).
• Monitoring: emitted IDs/ms, sequence saturation, clock-skew events.

Trade-offs

• Snowflake: short, ordered, needs coord for worker ID.
• UUIDv4: zero coord, 128-bit storage cost, hurts index locality (random inserts in B-trees).
• UUIDv7 / ULID: best of both for modern systems.
• DB sequence: simplest, but central; OK up to ~10k inserts/s.
• Range allocator (Leaf-segment): claim block of 1k IDs at a time → 1k× fewer ZK trips.

Refs

• Twitter Snowflake (2010 blog), Discord "How Discord Stores Billions of Messages", Meituan Leaf paper, Instagram Engineering "Sharding & IDs", RFC 9562 (UUIDv7).