Can't speak for SBCL (I use it exclusively for development and haven't deployed anything non trivial and user facing with it) but I have used Clozure CL (CCL) s

Can't speak for SBCL (I use it exclusively for development and haven't deployed anything non trivial and user facing with it) but I have used Clozure CL (CCL) successfully to develop back end services without horror stories regarding the GC. If you end up needing huge heap sizes, in theory with ABCL you get access to state of the art GC algorithm implementations and (IMHO) a much nicer, less dogmatic language than Clojure. I recently switched to LispWorks after struggling a bit with CCL's Cocoa bridge and I wish I had done that sooner. A much younger, idealistic me would scream at the thought of it but sometimes you just need to throw some money at a problem. CAPI is really a killer feature.