Using elasticsearch as a cache with frequent updates

We are considering to use ES as a cache, for storing about 100K documents and updating them every 1 minute.
The size of each document is very small, containing 10-20 text fields.

We would like to know whether ES can support such an update scenario.
Should we worry about memory fragmentation over time, resulting in performance deterioration, assuming that the volume of updates supersedes the volume of searches by a big order of magnitude?

I would probably use 2 indices and an alias.

Index in the cold index, switch the alias,
delete the new cold index.