There's two groups of people who need to squeeze all the work out of every cycle they can get: Embedded programmers (which, despite our massively powerful phone processors, still includes mobile due to power issues), and cloud programmers. Cloud people are totally interested in optimizing everything to within an inch of its life, so it's a valid concern for them that even if they reduce their user space costs to 0 they still have limits put on them by the kernel. And cloud people are willing to put a lot of cleverness and work into their core pathways, and will get surprisingly close to the minimum time necessary, so you might be surprised how much they can get done in fractions of a microsecond in their core workload.
You may not have these problems, in which case in addition to "the concept of redis" baffling you, this will seem absurdly performance-sensitive to you. From a desktop programmer or all but the most complicated websites, that is also a sensible perspective. But the niche in which this discussion makes perfect sense is itself pretty large.
Game developers also belong to that group of people who squeeze work out of every cycle. Less than 18 months ago, two of the most commonly used devices contained:
512MB dedicated RAM (with 10MB of VRAM) (xbox 360) and
256MB RAM and 256MB VRAM (PS3)
alongside very aged processors. The hardware was almost 10 years old in both cases. Even the current gen aren't particularly powerful, coming in at 8GB ram with a 1.75GHz processor, and a GPU comparable to a 3-4 year old PC for the xbox one, and 1.6GHz processors, 8GB ram and a slightly beefier GPU in the case of the PS4.
You may not have these problems, in which case in addition to "the concept of redis" baffling you, this will seem absurdly performance-sensitive to you. From a desktop programmer or all but the most complicated websites, that is also a sensible perspective. But the niche in which this discussion makes perfect sense is itself pretty large.