Divio Cloud projects use Postgres as their database engine. We have chosen Postgres because it is widely regarded as the most reliable and high-performance relational database suitable for Django projects, and our many years of experience with various database systems bear this out.
By default, new projects will be provisioned with Postgres 9.6 databases.
At present we don't intend to provide alternative database backends. However, if you absolutely must have MySQL or another database system on your project, please get in touch for a quotation for a custom implementation.