title: nosql storage for tracking user behavior
body: <p>I'm trying to develop a system with records user actions on our site so later on we can make some patterns. I'm not sure what data storage should I use, but I consider something NoSQL like because it's easy scalable. It should be something schemaless, so we can easy change data format if necessary. Also, it should write data pretty fast and often, but reads are done very rare. </p>
  
  <p>Data should be something like this:</p>
  
  <p>userid=1,action=act1,timestamp=1234, additional_info1=something_here
  userid=2,action=act1,timestamp=324, additional_info2=something_else_here</p>
  
  <p>Upon storage, we want to make some statistics for one user, one action, one additional_info.</p>
  
  <p>Can you give me some hints on what storage should I use?</p>
  
  <p>PS: Out webapp is written in PHP</p>