Maybe you are right, but until it's not a part of the Oxwall default release I'm going to develop this plugin.

No problem with explanation:

"- the plugin regularly optimizes database tables and does it automatically on schedule" - the plugin runs Optimize query for every table by schedule, this helps to avoid space overhead and increase table index speed.

"- the plugin caches up to 30% of database queries within predefined lifetime which makes your page load faster" - the plugin uses external storage (memcached, apc) to store query results. Both of them are much faster then executing mysql query, so it's not a cache available out of the Mysql box.

yes it is great you did this plugin while it is missing from default oxwall installation; thank you.

thanks for clarifying the rest of the questions