diff --git a/make_post_sell/lib/karaoke.py b/make_post_sell/lib/karaoke.py
index d5eafe2..431ae5d 100644
--- a/make_post_sell/lib/karaoke.py
+++ b/make_post_sell/lib/karaoke.py
@@ -234,7 +234,7 @@ def backfill_karaoke_async(shop_id, session_factory, app_settings):
             # Query account concurrency from unsandbox API — abort if keys are bad
             try:
                 key_info = validate_keys(pk, sk)
-                concurrency = max(1, int(key_info.get("concurrency", 1)))
+                concurrency = min(2, max(1, int(key_info.get("concurrency", 1))))
             except Exception as e:
                 log.error("Backfill aborted — unsandbox keys invalid or expired for shop %s: %s", shop.name, e)
                 return