First, check what the performance hit is to read the config info from the db everytime you need it. If you have a low-volume sight, or you are hitting the db to serve the page anyway, you may not notice the overhead.

Another solution is to keep the timestamp in your config hash and then decide to refresh from the db every "n" minutes regardless. Then the performance his occurs on a small fraction of the requests.

You could (through stored procedures or your maint page), write the config info to the file system. Then either every request, or comparing timestamps on the file and the hash, refresh as needed.

Or set the apache children to die after "n" requests and when they initalize they can get the current config, etc.