diff --git a/docs/development/extensions-core/lookups-cached-global.md b/docs/development/extensions-core/lookups-cached-global.md
index 585e6f9a983..a2b69950212 100644
--- a/docs/development/extensions-core/lookups-cached-global.md
+++ b/docs/development/extensions-core/lookups-cached-global.md
@@ -368,6 +368,12 @@ The JDBC lookups will poll a database to populate its local cache. If the `tsCol
 }
 ```
 
+> If using JDBC, you will need to add your database's client JAR files to the extension's directory.
+> For MySQL, you can get it from https://dev.mysql.com/downloads/connector/j/, and for Postgres, from
+> https://jdbc.postgresql.org/download.html or from `extensions/postgresql-metadata-storage/`.
+> Copy or symlink the downloaded file to
+> `extensions/druid-lookups-cached-global` under the distribution root directory.
+
 ## Introspection
 
 Globally cached lookups have introspection points at `/keys` and `/values` which return a complete set of the keys and values (respectively) in the lookup. Introspection to `/` returns the entire map. Introspection to `/version` returns the version indicator for the lookup.