diff --git a/backend/danswer/background/update.py b/backend/danswer/background/update.py
index 5ec8b4770..586ed2d8d 100755
--- a/backend/danswer/background/update.py
+++ b/backend/danswer/background/update.py
@@ -37,6 +37,7 @@ from danswer.db.models import Connector
 from danswer.db.models import IndexAttempt
 from danswer.db.models import IndexingStatus
 from danswer.search.search_utils import warm_up_models
+from danswer.utils.acl import set_acl_for_vespa_nonblocking
 from danswer.utils.logger import IndexAttemptSingleton
 from danswer.utils.logger import setup_logger
 
@@ -452,6 +453,12 @@ def update_loop(delay: int = 10, num_workers: int = NUM_INDEXING_WORKERS) -> Non
         # This ensures that bad states get cleaned up
         mark_all_in_progress_cc_pairs_failed(db_session)
 
+    # TODO: remove this once everyone is migrated to ACL
+    # does nothing if this has been successfully run before
+    # NOTE: is done in another thread, to not block indexing runs from
+    # getting kicked off
+    set_acl_for_vespa_nonblocking(should_check_if_already_done=True)
+
     while True:
         start = time.time()
         start_time_utc = datetime.utcfromtimestamp(start).strftime("%Y-%m-%d %H:%M:%S")
diff --git a/backend/danswer/main.py b/backend/danswer/main.py
index 5b2d1a06e..24d4e99fc 100644
--- a/backend/danswer/main.py
+++ b/backend/danswer/main.py
@@ -43,7 +43,6 @@ from danswer.server.search_backend import router as backend_router
 from danswer.server.slack_bot_management import router as slack_bot_management_router
 from danswer.server.state import router as state_router
 from danswer.server.users import router as user_router
-from danswer.utils.acl import set_acl_for_vespa
 from danswer.utils.logger import setup_logger
 from danswer.utils.variable_functionality import fetch_versioned_implementation
 
@@ -197,11 +196,6 @@ def get_application() -> FastAPI:
         logger.info("Verifying Document Index(s) is/are available.")
         get_default_document_index().ensure_indices_exist()
 
-        # TODO: remove this once everyone is migrated to ACL
-        logger.info("Populating Access Control List fields in Vespa")
-        # does nothing if this has been successfully run before
-        set_acl_for_vespa(should_check_if_already_done=True)
-
     application.add_middleware(
         CORSMiddleware,
         allow_origins=["*"],  # Change this to the list of allowed origins if needed
diff --git a/backend/danswer/utils/acl.py b/backend/danswer/utils/acl.py
index d88b1cff8..bed2683f8 100644
--- a/backend/danswer/utils/acl.py
+++ b/backend/danswer/utils/acl.py
@@ -1,3 +1,5 @@
+from threading import Thread
+
 from sqlalchemy import select
 from sqlalchemy.orm import Session
 
@@ -33,6 +35,7 @@ def set_acl_for_vespa(should_check_if_already_done: bool = False) -> None:
     if not isinstance(vespa_index, VespaIndex):
         raise ValueError("This script is only for Vespa indexes")
 
+    logger.info("Populating Access Control List fields in Vespa")
     with Session(get_sqlalchemy_engine()) as db_session:
         # for all documents, set the `access_control_list` field apporpriately
         # based on the state of Postgres
@@ -52,3 +55,11 @@ def set_acl_for_vespa(should_check_if_already_done: bool = False) -> None:
         )
 
     dynamic_config_store.store(_COMPLETED_ACL_UPDATE_KEY, True)
+
+
+def set_acl_for_vespa_nonblocking(should_check_if_already_done: bool = False) -> None:
+    """Kick off the ACL update in a separate thread so that other work can continue."""
+    Thread(
+        target=set_acl_for_vespa,
+        args=[should_check_if_already_done],
+    ).start()