Unique IDs at Scale

Generating IDs without coordination: UUIDv4 (random; poor index locality), UUIDv7 (RFC 9562; time-ordered prefix + randomness — good B-tree locality, sortable), ULID (similar, Crockford base32), Snowflake (64-bit: timestamp + machine + sequence; compact, needs machine IDs), and database sequences (simple, central). Prefer UUIDv7 for most new systems; Snowflake when you need 64-bit integers.

ID schemes

import uuid
order_id = uuid.uuid7()          # Python 3.14+: time-ordered RFC 9562 UUIDv7
# earlier versions: use a library such as uuid6/uuid-utils

-- PostgreSQL 18+: built-in uuidv7()
CREATE TABLE orders (id uuid PRIMARY KEY DEFAULT uuidv7(), created_at timestamptz DEFAULT now());

import { v7 as uuidv7 } from "uuid";
const orderId = uuidv7();          // sortable by creation time

Common pitfalls

• Random UUIDv4 primary keys on huge B-tree tables (write amplification).
• Exposing sequential IDs publicly (enumeration).
• Snowflake with duplicate machine IDs.

Key points

• UUIDv7 as a modern default
• Snowflake for 64-bit needs
• Don't expose enumerable IDs

Further reading: RFC 9562: UUIDs (including v7)