To support a new database engine type you will need to modify or add to the following files. You might, for example want to integrate percona or mongodb and so on.

adt-autoscaler-scripts/autoscaler/InitialiseCloudInit.sh

adt-build-machine-scripts/builddescriptors/buildstyles.dat
adt-build-machine-scripts/initscripts/InitialiseCloudInit.sh
adt-build-machine-scripts/initscripts/InitialiseDatabaseService.sh
adt-build-machine-scripts/providerscripts/application/moodle/SetApplicationConfig.sh
adt-build-machine-scripts/providerscripts/security/firewall/TightenDBaaSFirewall.sh
adt-build-machine-scripts/templatedconfigurations/quick_specification.dat
adt-build-machine-scripts/templatedconfigurations/specification.md

adt-database-scripts/applicationdb/*
adt-database-scripts/installscripts/InstallDatabaseClient.sh
adt-database-scripts/installscripts/InstallDatabaseServer.sh
adt-database-scripts/providerscripts/database/*
adt-database-scripts/providerscripts/utilities/remote/*
adt-database-scripts/providerscripts/utilities/status/IsDatabaseUp.sh

adt-webserver-scripts/installscripts/InstallDatabaseClient.sh
adt-webserver-scripts/installscripts/InstallMySQLClient.sh
adt-webserver-scripts/providerscripts/application/configuration/drupal/InitialiseVirginInstall.sh
adt-webserver-scripts/providerscripts/application/configuration/joomla/InitialiseVirginInstall.sh
adt-webserver-scripts/providerscripts/application/configuration/moodle/InitialiseVirginInstall.sh
adt-webserver-scripts/providerscripts/application/configuration/wordpress/InitialiseVirginInstall.sh
adt-webserver-scripts/providerscripts/application/processing/drupal/CheckInstalled.sh
adt-webserver-scripts/providerscripts/application/processing/drupal/CheckUser.sh
adt-webserver-scripts/providerscripts/application/processing/drupal/TruncateCache.sh
adt-webserver-scripts/providerscripts/utilities/remote/ConnectToRemoteMySQL.sh
adt-webserver-scripts/providerscripts/utilities/status/CheckServerAlive.sh
adt-webserver-scripts/ws.sh