Every order requires a globally unique, time-sortable Order ID. Multiple services across regions generate IDs simultaneously. How would you design this?

IDsDistributed SystemsSystem DesignMulti-Region

How I frame it

Clarify scale (orders/sec), multi-region requirement, and whether IDs are customer-facing or internal. Sortable IDs help sharding, analytics watermarks, and support "show orders after this time" without a global sequence bottleneck.

Requirements

Globally unique — no collision across regions/services.
Time-sortable — support queries "orders after T" without central sequence.
High throughput — no single DB bottleneck per ID.

Snowflake-style 64-bit ID

Bits: timestamp_ms | datacenter_id (5) | machine_id (5) | sequence (12). ~4096 IDs/ms per machine. Sortable by time; unique if machine IDs assigned via config service / K8s StatefulSet.

Clock backward NTP jump: Wait until caught up or use last timestamp.
Sequence overflow in 1ms: Block until next millisecond.
Alternatives: UUIDv7, ULID — standard libraries, good enough for most e-commerce.

EU order service + US order service
  Each has unique (dc_id, machine_id)
  No coordination per ID generation
  IDs sort ≈ creation time for sharding

When not Snowflake

DB sequence per shard adds coordination latency. Human-readable order numbers may use separate display id + internal snowflake.

Walkthrough

US order service (machine 12) and EU order service (machine 87) both create orders at 14:00:00.001. Snowflake IDs share timestamp prefix — sortable in global order feed. No central DB sequence bottleneck. Support queries orders WHERE id > last_id for incremental sync to warehouse.

Weak answer

"Auto-increment in MySQL." Single-writer bottleneck; not multi-region friendly. "UUID v4" — unique but not time-sortable; bad for range queries and sharding hot spots.

Follow-up questions

Machine id collision after autoscale?

Lease machine_id from ZooKeeper/etcd on pod start; release on shutdown. Or embed pod UID in id scheme.

Privacy — ID leaks order volume?

Public-facing opaque token separate from internal sortable id.