# Internals

- [Database Design](/guides/internals/database-design.md)
- [Internationalization (i18n)](/guides/internals/internationalization-i18n.md)
- [Rake](/guides/internals/rake.md)
- [Testing](/guides/internals/testing.md)
- [Upgrading](/guides/internals/upgrading.md)
- [Creating extensions](/guides/internals/creating-extensions.md)