Mysql Replication - How it works offline?
Replication sounds like what you need, as long as the slave server you envision will be used as read-only.

Connecting a slave (replica) server to a master imposes very little load on the master.  If the connection between the two is severed for whatever reason, the slave will continue to answer queries, and normally will reconnect to the master as soon as practical and pick up exactly where it left off.  Certain disruptions can cause you to have to take steps to get replication going again, but ordinarily this is automatically done.

Using a replica this way is common.  

I produce several hundred scheduled reports every day, many of which evaluate many millions of rows... and the reports are run against slave servers, to relieve the master of this additional workload.  In some cases, the slave is many thousands of miles away from the master, so, naturally, the connections are periodically lost... but they restart themselves.