diff --git a/aleph.env.tmpl b/aleph.env.tmpl
index 58baddfc5..596221241 100644
--- a/aleph.env.tmpl
+++ b/aleph.env.tmpl
@@ -91,6 +91,10 @@ ALEPH_OAUTH_SECRET=
 # Define a different ftm entity store:
 # FTM_STORE_URI=postgresql://<username>:<password>@<host>/<database>
 
+# ingest-file uses a document cache to speed up operations
+# (it defaults to either one of the two above postgres connection strings)
+# TAGS_DATABASE_URI=postgresql://<username>:<password>@<host>/<database>
+
 # Queue mechanism
 # REDIS_URL=redis://redis:6379/0
 # RABBITMQ_URL=rabbitmq