It would require a little more setup, but you could minimize ram requirements and processing if you ran one nodeos dedicated to RPC requests (minus push_transaction) with the filter-on = * for history_plugin and read-mode = head.

And ran another for handling push_transaction without the filter-on = *. This of course would require a proxy to route the requests.

Update: Actually a proxy is not necessary as nodoes will forward on the transaction to other nodeos.