I think the Unix philosophy of "do one thing and do it well" applies here. There are already off-the-shelf caching solutions that do what you describe: for exam

I think the Unix philosophy of "do one thing and do it well" applies here. There are already off-the-shelf caching solutions that do what you describe: for example, with Varnish you can serve cached pages immediately and update the cache contents in the background. It would probably be better to use those than reimplement them in an uber-webapp.