Pricing snapshots: time-travel queries

Design a Postgres schema for a multi-tenant events ledger. Expected 1B rows. 90-day retention. Reads dominate by (tenant_id, time-range).

Audit log: immutable, GDPR-friendly purge

IoT telemetry, 1M devices, columnar fits

Multi-tenant feature flags, 10k tenants

User activity log: 50M rows/day, 7d hot retention