If the main mysql (A), from (B) On the domestic, from (C) placed abroad.
Reading: Reading domestic read from the database b, c abroad to read from the database. Each reading is acceptable.
Write: A very quick to domestic and foreign A written will be very slow (this may be acceptable).
However, when the data is synchronized to the A C servers abroad, there will be long delays, if at the beginning of the synchronization is not over when the foreign data access, there will be a cache (memcached), the cache is old data. However, after the end of synchronization, data in the database is up to date, but the cache is old data, there has been inconsistent data.
Like the East Coast and the West Coast of data synchronization facebook.
http://shiningray.cn/facebook-scaling-out.html
However, we are a small team, you do not modify the mysql. I ask, is there any alternative to this solution.