diff --git a/client/src/app/+videos/+video-edit/video-add-components/video-upload.component.ts b/client/src/app/+videos/+video-edit/video-add-components/video-upload.component.ts
index f383662a1a9c..003e1a5821d0 100644
--- a/client/src/app/+videos/+video-edit/video-add-components/video-upload.component.ts
+++ b/client/src/app/+videos/+video-edit/video-add-components/video-upload.component.ts
@@ -73,9 +73,10 @@ export class VideoUploadComponent extends VideoSend implements OnInit, OnDestroy
       token: this.authService.getAccessToken(),
       uploaderClass: UploaderXFormData,
       retryConfig: {
-        maxAttempts: 6,
-        shouldRetry: (code: number) => {
-          return code < 400 || code >= 501
+        maxAttempts: 30, // maximum attempts for 503 codes, otherwise set to 6, see below
+        maxDelay: 120_000, // 2 min
+        shouldRetry: (code: number, attempts: number) => {
+          return code === HttpStatusCode.SERVICE_UNAVAILABLE_503 || ((code < 400 || code > 500) && attempts < 6)
         }
       }
     }
diff --git a/server/lib/redis.ts b/server/lib/redis.ts
index a3a8727922b5..69a9327db347 100644
--- a/server/lib/redis.ts
+++ b/server/lib/redis.ts
@@ -207,7 +207,7 @@ class Redis {
 
   setUploadSession (uploadId: string, video?: { id: number, uuid: string }) {
     return this.setObject(
-      uploadId,
+      'resumable-upload-' + uploadId,
       video
         ? {
           id: video.id.toString(),
@@ -219,11 +219,11 @@ class Redis {
   }
 
   doesUploadSessionExist (uploadId: string) {
-    return this.exists(uploadId)
+    return this.exists('resumable-upload-' + uploadId)
   }
 
   getUploadSession (uploadId: string) {
-    return this.getValue(uploadId)
+    return this.getValue('resumable-upload-' + uploadId)
   }
 
   /* ************ Keys generation ************ */
diff --git a/server/middlewares/validators/videos/videos.ts b/server/middlewares/validators/videos/videos.ts
index 7d440e2101b8..74d01d3f902c 100644
--- a/server/middlewares/validators/videos/videos.ts
+++ b/server/middlewares/validators/videos/videos.ts
@@ -121,7 +121,7 @@ const videosAddResumableValidator = [
       if (!sessionResponse) {
         res.setHeader('Retry-After', 300) // ask to retry after 5 min, knowing the upload_id is kept for up to 15 min after completion
         res.fail({
-          status: HttpStatusCode.CONFLICT_409,
+          status: HttpStatusCode.SERVICE_UNAVAILABLE_503,
           message: 'The upload is already being processed'
         })
       } else {
diff --git a/support/doc/api/openapi.yaml b/support/doc/api/openapi.yaml
index f43943ec139f..36555e0cd02f 100644
--- a/support/doc/api/openapi.yaml
+++ b/support/doc/api/openapi.yaml
@@ -2039,11 +2039,18 @@ paths:
         '404':
           description: upload not found
         '409':
-          description: chunk doesn't match range or upload being processed
+          description: chunk doesn't match range
         '422':
           description: video unreadable
         '429':
           description: too many concurrent requests
+        '503':
+          description: upload is already being processed
+          headers:
+            'Retry-After':
+              schema:
+                type: number
+                example: 300
     delete:
       summary: Cancel the resumable upload of a video, deleting any data uploaded so far
       description: Uses [a resumable protocol](https://github.com/kukhariev/node-uploadx/blob/master/proto.md) to cancel the upload of a video