Tempo, Rhythm and Timing are not the same thing.

Tempo refers to the speed of the swing (takeaway, backswing and downswing until impact).
Rhythm refers to the speed change during the various phases of the golf swing movement. The goal is to swing with grace. So avoid that your swing becomes a series of movements. All the parts of your swing must work together in harmony.
Timing is independent of rhythm and tempo; it refers to the succession of body and club movements, and that should happen in a proper sequence in order to deliver consistent results.
The "Swing Ratio" refers to the ratio of the measured time in seconds it takes to make the backswing, on the measured time in seconds it takes to make the downswing until impact.
Unfortunately, everyone does not use these terms correctly.

A swing ratio of 3:1 means the backswing is three times as long as the downswing. This swing ratio can vary across club selection or shot type. For example, many touring pros use a swing ratio of 3:1 for their driver with a ratio of 2.1:1 when making their putts.

Tempo, Rhythm, Timing: These features of a good golf swing have not received the attention they deserve. Recently a whole new awareness of their significance was created by the book, Tour Tempo, written by John Novosel.

What is Tempo: The word “tempo” is used to define the amount of time that elapses from the beginning of the takeaway until impact. We must understand how a pendulum behaves, and understand how not to disrupt that natural behavior of your pendulum propertied golf club is the principal point of this instruction. It must be a cooperation with Gravity and not a fight against, either by applying force wrongly to the club shaft, or by applying force in the right way but at the wrong time, so as to interfere with momentum, to fight with rather than use its inertia! A pendulum swing demands our respect, based on realizing what happens when its smooth back and forth action is or is not disrupted by inappropriated forces.

Transitions: The critical parts of your golf swing are where you or your club changes direction – in what are called “the transitions – and that’s plural because in addition to the one that’s recognized by everyone that occurs when the backswing ends and the downswing is to begin, there’s another that needs also to be recognized and respected. That’s the one used to start the swing itself, a gentle and small weight shift from a position in which your body is balanced about equally between both feet to one where your weight slightly favors your left foot.

This weigh shift, creating imbalance in the body, triggers a change in how we conduct our mental processes: in preparation for a swing, several cognitive issues are on the table, such as club selection, body alignment, ball position, grip, posture, stance, etc... But once athletic action is to occur to be activated the same as occurs when we turn on an electric switch, we need to tap largely into our "Neuromuscular Automatic Response" which is the state in which we react with instinct and without thought  in the same manner as it works for us to “get a coffee” without ever having the slightest concern for what we do with our hands, fingers, elbows, knees, or feet: WE JUST DO IT.

So the transition to start the swing itself acts not only to get things moving, but it shifts our focus to the job at hand which defies active “thinking” and accesses the genius built in to our neuro-muscular.

Managing your motion: The next part of it, the other transition for beginning the downswing, is the beginning of the return of the body’s mass onto the left leg, followed by the hovering club beginning its fall down. When the club and arms are swung back with the right amount of force to take them as far as is appropriate for the shot desired, the body itself also reacts to the imbalance of more weight on the right leg than the left, and because of that, it senses how it must fall back to the left.

The sequence is this: shortly before the hands start to fall, the golfer’s body weight falls back to the left under a steady head—a shift often experienced as a hip bump or slide, sometimes wrongly reported as a hip turn. (Later in the downswing it will be followed seamlessly by a turn, but the initial movement is a sideways motion of the hips of a few inches.)
Conclusion: The main point is to wait for gravity to start moving the swing, and then to help it, all without bullying the swing with insensitive inappropriate bluntness.

Nearly everyone starts downswing too early, even after having been cautioned repeatedly, and only by experimenting "waiting too long" before starting downswing will anyone  make discover and sense how long is a natural transition. so you cannot swing too fast, you just swing too early!