(to_lisp);
(loop for i below 1000000 count t) takes 0.34 seconds on my system with vanilla maxima (on gcl). In the browser it takes about 7 seconds, so it must be a factor of 21 in computer time. Using sbcl outside maxima it takes 0.002 seconds. So one can get some idea about performance.
Perhaps it could be combined with J (array language), like in the playground https://code.jsoftware.com/wiki/Playground that is using webassembly
It seems to work very well locally without connection to the web.