Model a situation (to change which, as usual, is not possible). Using memcached (Memcache is used by clientd in PHP) are stored, for example, quotes (text or even binary, but base64).
The keys are numbers of citations. Value — text citations. The numbers of the citations is inconsistent. That is, first to add quotes with numbers 100 and 101, and then 18, 25 and 204, while other quotes may not be at all. Quotes — thousands.
Not all that lies in store quotes. In addition to quotes in the repository there are a few (very few units) other values, but their keys are known in advance.
Problem: display random quote from storage.
Prompt, please, the most elegant solution with minimal reshaping of the existing economy.