Replication over Distributed Datacenters

I have a setup where I have the main DB in Frankfurt and a replica in Sao Paulo. I found that accessing the site from the replica is extremely slow, even for read access like showing the blog. I suspect that the object caching is the problem, since it is written to the options table. Can I add a Redis object caching on such a distributed setting? Is it going to cause any other problem for me?