What is system.billing.usage? · Ultra Transcenders glossary

The system table to build cost queries on, covering billable usage for the whole account. Records usually appear within 12 hours.

In the Ultra Transcenders books

Each book explains system.billing.usage in context, with comparison tables and the common traps.

Chat message roles
Labels on chat messages: instructions go under system, the person's input under user, the model's previous answers under assistant, and results returned by a called tool under tool (or function).
Event
Table in Log Analytics where entries from Windows event logs are kept.
total_tokens
The usage field that sums prompt_tokens and completion_tokens, for example 37 + 86 = 123. Billing applies to both kinds of token.

Billing tables
The system tables that show charges: system.billing.usage lists billable use in DBUs and system.billing.list_prices lists the prices. Request and token counts live in usage tables instead.
record_type
Tells you the nature of a row in system.billing.usage, because fixes are added rather than edited in place. ORIGINAL is the first record, RETRACTION reverses a wrong one with a negative quantity, and RESTATEMENT supplies the right figures.
Serverless usage policy
A Public Preview feature that automatically attaches custom tags to the serverless notebooks, jobs, pipelines and serving endpoints a user runs, letting their cost be traced in system.billing.usage and budgets. Classic compute isn't tagged by it.
System tables
Operational data about your account, held read-only in the system catalog, e.g. system.access.audit, system.billing.usage and lineage. Users need SELECT plus USE CATALOG and USE SCHEMA.