This is the default example configuration of lmdb provided by Postfix. This config file was generated by Postfix running on Alpine 3.
It is located under: /etc/postfix/dynamicmaps.cf.d/lmdb
lmdb postfix-lmdb.so dict_lmdb_open mkmap_lmdb_open
Download the raw file with wget or curl
wget -O lmdb.example http://exampleconfig.com/static/raw/postfix/alpine3/etc/postfix/dynamicmaps.cf.d/lmdb
curl http://exampleconfig.com/static/raw/postfix/alpine3/etc/postfix/dynamicmaps.cf.d/lmdb > lmdb.example
Other config files you might find useful