title: database that allows to read and write from mutable array by index
body: <p>I'm looking for a database that allows me to store and retrive strings by an index. It should work just like a mutableArray but on disk. The database entries have a fixed length, the number of entries grows over time, up to about 100'000'000.  </p>
  
  <p>It doesnt matter if its sql, nosql or something else. The random read and writes should just be fast. I have had a look at levelDB and Kyoto but they store by key and not by array index. </p>
  
  <p>Any hints are very much appreciated. </p>