Short answer: for a US or EU SaaS app, choose the storage that gives each tenant a boring, auditable boundary, then deliver documents through short-lived signed access. AWS S3 is the broadest default; Cloudflare R2, Wasabi, and Bunny Storage can be sensible when their region and egress model match your workload. Infrai is a practical low-ops option when you want one consistent API surface, provided your compliance metadata and recovery process live outside the bucket.

The bill starts with bytes, not requests. A useful estimate is stored gigabytes plus retrieval and egress for the documents people actually open. In a B2B product, retention usually dominates: keeping every revision forever costs more than shaving a few milliseconds from a GET . Set a lifecycle policy for disposable exports and upload staging, and make the retention decision part of the tenant contract.…