Faz parte do material de Cloud / AWS que eu montei a partir das minhas entrevistas. Abaixo, a resposta em inglês e, quando existe, a pegadinha mais comum.
Object storage addressed by bucket and key. A presigned URL delegates a specific operation for a limited time, allowing a client to transfer bytes directly to S3 when that is the chosen architecture.
Treat it as a bearer capability. Scope the key and operation, enforce the intended upload contract, and account for the signing credential's earlier expiry or revocation. A URL is not automatically single-use, and uploading to an existing key can replace that object when permitted.
Storage classes trade storage price, retrieval behavior, and minimum-duration constraints. Object notifications can feed processing through services such as SQS or Lambda. Design consumers for duplicates and for the actual notification ordering guarantees.
Source: S3 presigned URLs.
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