title: Is there any good known solution for a fast persistent cache?
body: <p>I need really fast and persistent cache for my web crawler. It doesnt need to be as fast as ConcurrentSkipListSet in Java, but definitely it cannot be MySQL with hash-index based table, which i tried. After 1m+ of records it takes like 80% of processor time.
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  Does any one know or heard of something useful for this case?<br>
  Thanks for any hint.<br><br></p>