## H.4. Extensions

Postgres Pro is designed to be easily extensible. For this reason, extensions loaded into the database can function just like features that are built in. The `contrib/` directory shipped with the source code contains several extensions, which are described in Appendix F, Additional Supplied Modules. Other extensions are developed independently, like PostGIS. Even Postgres Pro replication solutions can be developed externally. For example, Slony-I is a popular master/standby replication solution that is developed independently from the core project.