When I have started to research internet to configure Loadbalancer in front of MongoDB cluster I couldn’t find easy and detailed documentation about that. But, I found ways how can I get status of the MongoDB cluster with the CLI. Due that I have started to think find way for some of the loadbalancer which, will send this command to each of the backend nodes, to understand is this master or slave node. From official documentation HAProxy I found this discussion and started to go deep inside. After research, as I understand there is not enough information about that. After success result of my work with 3 cluster of structured(PostgreSQL) and non structured(Redis, MongoDB) database, I have recorded video and all stuff to share my knowledge with everyone. I hope it will be useful to all of us.