it sounds to me that the jvm is not kept running and you are paying a startup cost each time.
Transpiling a bucket load of any language in a warm jvm will be less than 2-3 seconds, and could easily be done on page refresh.
to give you some perspective, we have massive closure apps, first compilation on my (very powerful) desktop takes a minute 30 seconds or so (advanced optimizations and several other extremely stringent flags along with quite a few compiler plugins we wrote) keeping the jvm warm, and compiling with these same flags + plugins, the time comes down to under 5 seconds.
