How about using a DB?

Could DokuWiki use a database instead of text files?

It would be possible, but there was a reason for not doing it. DokuWiki was designed to hold documentation of all kinds. So what do you do when your database or your web server is down and the documentation to bring it up again is only accessible through this web server or database? Yikes! So DokuWiki stores all this vital information as plain text which is always readable, even if you only have some tape backups left of your beloved Server .

http://www.pmwiki.org/wiki/PmWiki/FlatFileAdvantages talks about why flatfiles are better than databases for wikis of up to about 20,000 records.

Note that DokuWiki has built-in support for storing user authentication information in a database. See authentication backends.