diff --git a/backend/src/constants.py b/backend/src/constants.py
index 3e07f453..fd8d73c8 100644
--- a/backend/src/constants.py
+++ b/backend/src/constants.py
@@ -6,7 +6,15 @@
 PROD = os.getenv("PROD", "False") == "True"
 
 # 8001 emulates the data server
-BACKEND_URL = "https://api.statbotics.io" if PROD else "http://localhost:8001"
+# The ETL self-trigger (update_curr_year_background and the freshness-ping probe)
+# HTTP-calls BACKEND_URL to reach the data router. When the data router runs as a
+# separate service the default is right, but a single-container deploy (e.g. a
+# staging mirror serving all routers from one service) must point BACKEND_URL at
+# its OWN backend, or the self-trigger hits the wrong host and ingestion never
+# runs. Read it from the environment, falling back to the original default.
+BACKEND_URL = os.getenv("BACKEND_URL") or (
+    "https://api.statbotics.io" if PROD else "http://localhost:8001"
+)
 
 # DB