title: Redis - decrease TTL by single command
body: <p>Let's say I have redis record with TTL = 1 hour.</p>
  <p>Then some event occurs and I want to reset the TTL of this item to min(current-TTL, 5min). So it would decrease the TTL to 5 mins. if it is not already lower.</p>
  <p>The underlying use-case is, there can be too frequent invalidation of the cache and the &quot;old&quot; cache is almost as good as the fresh, if it is not older then 5mins. from the first change.</p>
  <p>I know I can fetch the TTL in one command and update it with second, but would prefer to set it by single command for various reasons. Is there a way?</p>
  <p>Edit: There will be many keys I would need to decrease by single command. So I would like to avoid data round-trips between redis and client library for each record.</p>