---
title: "2026-09-08 vxData batch presign NoSuchKey diagnosis"
description: "Production API logs showed directory prefixes were submitted as object URLs after a trailing slash was removed."
image: "https://docs.virdx.dev/img/virdx-social-card.png"
---

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# 2026-09-08 vxData batch presign NoSuchKey diagnosis

## Work Done

- Inspected the `vxdata-production` API pod with read-only `kubectl` commands.
- Found six `/s3/presign/batch` HTTP 500 responses between 09:09 and 09:14 UTC.
- Confirmed every failure was an uncaught MinIO `S3Error` with `NoSuchKey` while `with_sizes=True` caused `stat_object` to run on a domain-representation directory prefix.
- Traced the malformed URL to `diffsim/apps/gen4ve2e/generate_vxdata.py`: removing the full `"/gleason_seg.zarr/"` suffix also removes the directory prefix's trailing slash, so the SDK treats it as a single object rather than calling `/s3/list`.

## Lessons Learned: Pitfalls

- The infrastructure SOPs were useful for locating the production namespace, but no existing entry described the SDK's trailing-slash distinction for downloads.
- A batch endpoint failure can be misleading: one invalid item aborts the batch and surfaces as HTTP 500 even when batch presigning itself is healthy.

## Lessons Learned: Improvements

- Document that `vxd.storage.download` treats only S3 URLs ending in `/` as prefixes. Prefix URLs without `/` are presigned as objects and size lookup can raise `NoSuchKey`.
- The API should convert missing keys during presign into a clear 4xx response or a per-item batch error rather than an uncaught 500.

Source: https://docs.virdx.dev/knowledge/inbox/2026-09-08-infrastructure-vxdata-presign-nosuchkey/index.mdx