A design studio’s customer portal may receive a large artwork archive over an unreliable connection. Before commissioning resumable uploads, agree which parts are durable, which need retry and what proves the final object exists. A full progress bar is not that proof.
Primary evidence and claim boundaries
Cloudflare R2 documents multipart completion and resumable parts. Non-final parts have a5 MiB minimum and must share a size; incomplete uploads have their own lifecycle. Primary reference · Read 17 October 2026.
Filled acceptance example
Synthetic teaching scenario, not a client case, provider integration test or business result. Scroll the example table on narrow screens.
| Synthetic20 MiB archive | Part ledger | Required next step |
|---|---|---|
| Part 1 /8 MiB | Stored; ETagE1 retained | Keep part 1 |
| Part 2 /8 MiB | Connection lost; result unknown | Reconcile or retry part 2 under upload identity |
| Part 3 /4 MiB final | Stored; ETagE3 retained | Valid smaller final part in model |
| All parts later confirmed | Ordered completion manifest + final object readback | Verify size 20 MiB and content integrity |
Practical handover procedure
- Define object key, upload identity, byte size, part numbering and a secure authenticated ownership model. Use MiB consistently:20 MiB equals 20,971,520 bytes.
- Persist confirmed part references and distinguish unknown responses from confirmed failures. Check provider resume semantics rather than restarting the whole file automatically.
- Complete with the verified ordered part set, read the final object and verify the agreed checksum/size. Define abandoned-upload cleanup separately from completed-file retention.
Interpret the outcome
The part sizes sum to 20 MiB. Until part 2 and final completion are verified, the archive remains incomplete. An ETag should be treated according to the provider’s documented semantics, not assumed to be a universal whole-file checksum.
Acceptance decision
Demonstrate interrupted transfer, resumed part, final readback and abandoned-upload cleanup in an authorised test environment. Keep user upload permissions separate from transport success.
Limits and unverified work
Synthetic byte ledger only; no bucket, real file or cloud API was accessed. Actual request limits, quotas, lifecycle settings, malware review and confidentiality still need implementation evidence.
Download the filled bilingual acceptance record — Contains these inputs, steps, expectations and limits. This is a teaching record, not an executable integration.