Today go-to-definition across files takes a minute in large projects when a file isn't currently opened in an editor.

// a.ts
import "./b.js" // <- jump to definition on this path

// b.ts
export function foo() {
}

It's not clear why this is the case when the language service is fully initialized and program loading has occured - the file path is already known (even when declaration maps are enabled). So it seems like the editor is taking a bit longer than it needs, or go-to-definition is being blocked by some other operation (which should potentially be considered lower-priority).