diff --git a/br/pkg/lightning/backend/external/writer.go b/br/pkg/lightning/backend/external/writer.go
index 2cf86b5d99ba5..5cfd654335d5c 100644
--- a/br/pkg/lightning/backend/external/writer.go
+++ b/br/pkg/lightning/backend/external/writer.go
@@ -592,12 +592,12 @@ func (w *Writer) createStorageWriter(ctx context.Context) (
 	err error,
 ) {
 	dataPath := filepath.Join(w.filenamePrefix, strconv.Itoa(w.currentSeq))
-	dataWriter, err := w.store.Create(ctx, dataPath, &storage.WriterOption{Concurrency: 20, PartSize: (int64)(5 * size.MB)})
+	dataWriter, err := w.store.Create(ctx, dataPath, &storage.WriterOption{Concurrency: 10, PartSize: (int64)(5 * size.MB)})
 	if err != nil {
 		return "", "", nil, nil, err
 	}
 	statPath := filepath.Join(w.filenamePrefix+statSuffix, strconv.Itoa(w.currentSeq))
-	statsWriter, err := w.store.Create(ctx, statPath, &storage.WriterOption{Concurrency: 20, PartSize: (int64)(5 * size.MB)})
+	statsWriter, err := w.store.Create(ctx, statPath, &storage.WriterOption{Concurrency: 10, PartSize: (int64)(5 * size.MB)})
 	if err != nil {
 		_ = dataWriter.Close(ctx)
 		return "", "", nil, nil, err