title: memcache and elasticache autoscaling
body: <p>As far as I know if you implement autoscaling with memcached nodes and use some sort of dynamic trigger to include those new nodes in your app then you essentially invalidate the cache in doing so as you change the hash algorithm to assign shards. So if this is the case then load based autoscaling for memcached isn't a good idea. Is this correct?</p>
  
  <p>Does AWS Elasticache with auto discovery have some sort of smarts to stop this happening, as it supports adding nodes also and connects via a single IP? As far as I can see the answer is no, as it's essentially just altering configuration dynamically based on the server list in the discovery record, and thus will suffer the same problem, but hopefully someone more in the know than me can say either way.</p>
  
  <p>For background, I'm looking at AWS Opsworks and wondering whether to use Elasticache or a memcached layer.</p>