In the Ténéré, a desert region in south central Sahara, sand cats were observed preying foremost on small rodents, and the young of cape hare (Lepus capensis), but also hunting greater hoopoe lark (Alaemon alaudipes), desert monitor (Varanus griseus), sandfish (Scincus scincus) and venomous Cerastes vipers.
This paper claims that vipers and rattlesnakes have fastest strike rate
Mongoose are known predators of cobra.
These mammals are able to hunt them because of their faster reaction time and/or relex velocity.
So how is it that these animals have faster reaction times given that the length of signal transmission is actually lesser in those reptiles?
Myelin is considered a defining characteristic of the jawed vertebrates (gnathostomes), though axons are ensheathed by a type of cell, called glial cells, in invertebrates.
A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons.
So those factors are eliminated. For the mentioned case, it might be that those reptiles don't have as good of a perception as their predators but again they have a higher ratio of electrical:chemical synapses.
(In case of a fly it is probably the smaller body and electrical synapses)
So what are the general factors affecting the speed of a reflex/reaction time? If a specific system is of help, the visual reflex system of the feline will do just fine.
Why was the snake unable to escape being hit by the paw?
(The snake has an extremely fast strike velocity and the most likely factors are eliminated. At such close ranges, stimulus perception should not differ much either)