Per-tenant cost visibility changes the design: don't begin with parallel API calls; begin with a durable ledger that ties every classification result and usage record to a tenant, policy version, and source item. For a customer-support catalog backfill, the practical choice is a bounded Node.js worker that reads existing posts and comments, classifies them through a replaceable adapter, checkpoints each result, and exports tenant-scoped JSONL. Short answer: make the ledger the product of the ...