The entire thing is not complete so expect vulnerabilities, missing features and more scary stuff 👻.

Simple battleships game made in Express + vanilla DHTML (seriously).
It uses Redis as a store and Socket.io for connectivity. All the operations like ship position validating, shot validating and rooms are made server-side. It also integrates an e-mail authentication system (via OTPs) and stores persistent user data in MySQL. It has an integrated friends system with direct messaging and the ability to see your friends' statuses.