Introduction

A migration can move the application successfully while file writes still land in the old S3 bucket. The website may already run from the new environment, but uploads, exports, or generated assets continue going to the previous object-storage bucket because the application still uses an outdated bucket name, storage endpoint, or credential set.

Treat this as an object-storage target problem instead of a generic upload failure. Start by checking the exact bucket and endpoint the running application uses, because migrations often move compute or domains first while storage configuration quietly remains tied to legacy object storage.

Symptoms

  • The app still writes to the old S3 bucket after migration
  • Files upload successfully, but they appear in the previous bucket instead of the new one
  • The new environment works, but media, exports, or generated files remain split across old and new storage
  • Worker logs or application logs show writes to an unexpected bucket name or object-storage endpoint
  • One code path writes correctly while another still targets legacy object storage
  • The issue started after app migration, bucket cutover, or storage reconfiguration

Common Causes

  • The application still uses the old S3 bucket name or object-storage endpoint
  • Environment variables or secrets still point to the previous storage target
  • Background workers or file processors run with stale bucket configuration
  • The migration updated read paths or CDN URLs but not the live write destination
  • More than one storage client exists, and only one was updated after cutover
  • The old bucket still accepts writes, hiding the configuration mistake

Step-by-Step Fix

  1. Upload or generate a test file and confirm exactly which bucket and endpoint receive it, because you need the real write target rather than the storage design you expect to be active.
  2. Compare the live bucket name, region, and endpoint with the intended post-migration storage configuration, because one leftover reference can keep all new objects tied to the old bucket.
  3. Check application environment variables, secret values, storage client settings, and credential mappings for the active write path, because bucket drift often hides outside the main web configuration.
  4. Review workers, scheduled jobs, image processors, and secondary services that also write objects, because storage migrations often fix the main app while one background path still uses the previous bucket.
  5. Update the real active bucket target only after confirming the new bucket is writable, correctly permissioned, and used by the live environment, because changing storage settings without validation can break file handling entirely.
  6. Retest with a fresh write and verify the object now lands in the intended bucket, because the real fix is correct storage behavior rather than a successful config edit.
  7. Confirm the old bucket stops receiving new objects after the change, because continued writes to legacy storage reveal that one path still remains active.
  8. Review related CDN, signed URL, or object-processing paths if the application uses more than one storage workflow, because bucket migrations often leave secondary write paths behind.
  9. Document the final bucket ownership, write path, and credential scope after recovery, because object-storage targets are easy to overlook during future infrastructure migrations.