Aha,I don't stand by you coz,doesnot make sense at all!
Firstly, standby is a Word Noun,therefore,its a hack
secondly,stand by is a common short and fixed sentense which widely used in spoken English daily means support,help,just like,compare.to/related.to,tobeornottobe ect,they are fixed.
anyway,standby.com since 1995,.net 1997,.org,1997,.nl 1995,.be1998,.me2029.DK,1998 .co.uk 1997,co.nz 1998,us2004, and many more.
Whats more,many cctlds are on the run,like,.eu,.nl,,cz,de,pt,es,it,se and more
BTW,standby.by and standing.by are both taken ,standby.by since 2016 while standing.by since 2010