It’s true, Tracker is meant for client-side only. There are alternative approaches though, probably you’ll want to react to data changes, for which you can use cursor.observeChanges().
And technically, Tracker is usable in the server, it’s just that your autoruns need to be inside Meteor.bindEnvironment() (if you do things requiring to be Fiber-wrapped, like MongoDB operations).
Tracker.autorun(Meteor.bindEnvironment(function () {
myDependency.depend();
// Do reactive stuff...
}));