Thanks a lot!
Server is written in pure Java + Spring for http and Socket connectivity. Client is TypeScript and babylons as 3D graphic render engine. I didn't use any other dedicated software. Even have my own map editor (draft for now, but current game map along with collisions data was created with it). For sure it's not as optimal as possible but I'm really surprised about server performance, it's really good and are still stuff to optimise. Regarding client performance there's a one big thing to add which are Vertex Animations. This will improve performance a lot. Right now game works ok on regular computer but it can be much more efficient. - Will add plenty stuff to the game: environment, better skill effects etc so I'll need better performance.