@svetlana Yes, sandboxing is quick testing. And yes, you have it right, If you keep regular backups of mongo in that setup, you'll be fine (along with saving copy of your config, to be complete).
If you want to really be good at deploying and upgrades, then at the bare minimum you should know how git works, how to change node versions, and how to set up / back up mongo. Everything else has pretty much been scripted out. Most of this stuff is either in the wiki or on this forum, you just have to look a little 😉
@Nguyen-Nga That particular problem is due to a query we want to run against socket.io being unavailable in the latest version. It presents when used in a clustering setup, and the latest changes to NodeBB always have clustering active (even in a cluster setup of 1 process), so in the meantime it is difficult to get the data in question. This is why those graphs are not working at the moment.