When to mark function as async

Basically, function must be prefixed with async keyword if await used inside it. But if some function just returns Promise and doesn't awaiting for anything, should I mark the function as async?

Seems like both correct or not?

// with async (returns Promise)
async getActiveQueue() {
   return redisClient.zrangeAsync(activeQueue, 0, -1);
}

// difference? Both could be awaited isn't it?
getActiveQueue() {
   return redisClient.zrangeAsync(activeQueue, 0, -1);
}