Search and index weighted category tags / ratings, ideally in the plone directory

My use case is that content objects can have weighted tags:

• ArticleA: java 5, MySQL 3, php 1
• ArticleB: crypto 3, MySQL 2
• ArticleC: plone 5, network 1, security 4, agile 1
• ArticleD: plone4, MySQL3, php 3 ...

The list of tags is custom extensible, the range of values ​​is fixed, for example. fifteen

Now: how can I answer the following questions (ideally using portal_catalog):

• show all articles tagged java> 2 and MySQL> 3
• what is the average for MySQL
• What is the highest rated article?
• show all articles containing "foobar" and "plone"

Possible solutions that come to my mind or have been proposed so far:

• go SQL
• , ( )
• 'java3', 'java4', 'java5', KeywordIndex , AdvancedQuery [: , ( "", "Plone3", "Plone5" ) ]
• PluginIndex

, . , ( ) ?