This document discusses database replication including synchronous and asynchronous replication, master-slave and multimaster replication. It provides examples of implementing asynchronous master-slave replication in MySQL and PostgreSQL as well as asynchronous multimaster replication in CouchDB. The document notes some problems that can occur with multimaster replication including update conflicts and discusses potential solutions. Configuration steps are outlined for setting up basic replication between MySQL and PostgreSQL databases for learning purposes only and not for production use.