> Do they actually test both approaches, or is it more a matter of "we can code it way A or way B, and way A uses more memory, but we think it'll be faster"? A

> Do they actually test both approaches, or is it more a matter of "we can code it way A or way B, and way A uses more memory, but we think it'll be faster"? A lot of memory consumption is various caches (at various layers); those caches weren't added for no reason, they were added because they provided a demonstrable a perf gain.