title: Stack Overflow, Redis, and Cache invalidation
body: <p>Now that Stack Overflow uses redis, do they handle cache invalidation the same way?  i.e. a list of identities hashed to a query string + name (I guess the name is some kind of purpose or object type name).  </p>
  
  <p>Perhaps they then retrieve individual items that are missing from the cache directly by id (which bypasses a bunch of database indexes and uses the more efficient clustered index instead perhaps).  That'd be smart (the rehydration that Jeff mentions?).</p>
  
  <p>Right now, I'm struggling to find a way to pivot all of this in a succinct way.  Are there any examples of this kind of thing that I could use to help clarify my thinking prior to doing a first cut myself?</p>
  
  <p>Also, I'm wondering where the cutoff is between using a .net cache (System.Runtime.Caching or System.Web.Caching) and going out and using redis.  Or is Redis just hands down faster?</p>
  
  <p>Here's the original SO question from 2009:</p>
  
  <p><a href="https://meta.stackexchange.com/questions/6435/how-does-stackoverflow-handle-cache-invalidation">https://meta.stackexchange.com/questions/6435/how-does-stackoverflow-handle-cache-invalidation</a></p>
  
  <p>A couple of other links:</p>
  
  <p><a href="https://meta.stackexchange.com/questions/69164/does-stackoverflow-use-caching-and-if-so-how/69172#69172">https://meta.stackexchange.com/questions/69164/does-stackoverflow-use-caching-and-if-so-how/69172#69172</a></p>
  
  <p><a href="https://meta.stackexchange.com/questions/110320/stack-overflow-db-performance-and-redis-cache">https://meta.stackexchange.com/questions/110320/stack-overflow-db-performance-and-redis-cache</a></p>