diff --git a/api_service.py b/api_service.py
index c074c57..ceca917 100644
--- a/api_service.py
+++ b/api_service.py
@@ -5,7 +5,7 @@ This can run independently to support the PHP application
 import os
 import re
 
-from bibapi import catalogue
+# Avoid importing heavy modules at top-level to keep `import api_service` lightweight
 from fastapi import FastAPI, Query
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse
@@ -28,7 +28,9 @@ cat = None
 def _get_catalogue():
     global cat
     if cat is None:
-        cat = catalogue.Catalogue()
+        # import inside function to avoid expensive work during module import
+        from bibapi import catalogue as _catalogue
+        cat = _catalogue.Catalogue()
     return cat