Where and how is variable storage organized in the GitLab CI system?

In GitLab CI, variables are stored in several places and levels:

• Project Variables — set in the specific project's settings via the GitLab web interface. They are available in all pipelines of this project.
• Group Variables — set at the group level and available in all projects within this group.
• Environment Variables — can be defined in .gitlab-ci.yml for specific jobs or environments.
• Variables in the .gitlab-ci.yml file — can be defined using the variables key within the configuration file.

All these variables are stored in the GitLab database and can be encrypted (especially protected variables). During pipeline execution, GitLab Runner substitutes variable values into the container environment or runtime environment.

Thus, variable storage is organized centrally in GitLab and accessible for CI/CD processes through the environment.