mark LMDB backend experimental

diff --git a/docs/backends/lmdb.rst b/docs/backends/lmdb.rst
index 419899c9db45198331f78e19f6642ea5eed15dee..fd84cdcbda9e9d2d92520def3e30f684054a39b7 100644 (file)
--- a/docs/backends/lmdb.rst
+++ b/docs/backends/lmdb.rst
@@ -12,6 +12,10 @@ LMDB backend
 * Module name: lmdb
 * Launch name: ``lmdb``
 
+
+.. warning::
+  The LMDB backend is EXPERIMENTAL. Be prepared for incompatible changes between minor releases in the 4.2.x branch, and while tracking our git master.
+
 Enabling the backend
 --------------------