class Sprockets::Cache

def expand_key(key)

Returns a String with a length less than 250 characters.

key - JSON serializable key

Memcache.
The String should be under 250 characters so its compatible with

Internal: Expand object cache key into a short String key. 
def expand_key(key)
  "sprockets/v#{VERSION}/#{DigestUtils.pack_urlsafe_base64digest(DigestUtils.digest(key))}"
end