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MySQL has been having a lot of traction with customers, partners and developers in India. A very popular architecture for using MySQL for large scale deployments is the MySQL Master/Slave replication (Replication enables data from one MySQL database server (called the master) to be replicated to one or more MySQL database servers (slaves)).
Credit: Image is linked from http://dev.mysql.com/doc/refman/5.0/en/replication-solutions-scaleout.html.

One of things that change for developers, who are used to developing with other databases like Oracle, MS SQL server is the question on connecting to a MySQL master/Slave setup. There are several good resources which explain how to do this:
1. From MySQL web site: A snippet of the code from that article is reproduced below :

import java.sql.Connection;
import java.sql.ResultSet;
import java.util.Properties;

import com.mysql.jdbc.ReplicationDriver;

public class ReplicationDriverDemo {

  public static void main(String[] args) throws Exception {
    ReplicationDriver driver = new ReplicationDriver();

    Properties props = new Properties();

    // We want this for failover on the slaves
    props.put("autoReconnect", "true");

    // We want to load balance between the slaves
    props.put("roundRobinLoadBalance", "true");

    props.put("user", "foo");
    props.put("password", "bar");

    //
    // Looks like a normal MySQL JDBC url, with a
    // comma-separated list of hosts, the first 
    // being the 'master', the rest being any number
    // of slaves that the driver will load balance against
    //

    Connection conn =
        driver.connect("jdbc:mysql://master,slave1,slave2,slave3/test",
            props);

    //
    // Perform read/write work on the master
    // by setting the read-only flag to "false"
    //

    conn.setReadOnly(false);
    conn.setAutoCommit(false);
    conn.createStatement().executeUpdate("UPDATE some_table ....");
    conn.commit();

    //
    // Now, do a query from a slave, the driver automatically picks one
    // from the list
    //

    conn.setReadOnly(true);

    ResultSet rs = 
      conn.createStatement().executeQuery("SELECT a,b FROM alt_table");

     .......
  }
}

Note: Please refer to the mySQL web site for any updates.
2. If you are using Spring, Hibernate and other popular frameworks, an article at http://neilhan.blogspot.com/2006/11/spring-hibernate-and-mysql-replication.html tells you how to do it.