In our current upgrade documentation we do not mention the fact that Quay minor updates may contain database schema upgrades which are often preventing from a later downgrade once applied.

We should clarify our general upgrade policy:

• rollback or downgrades are generally not supported except between patch releases of a particular minor version, e.g. 3.7.2 -> 3.7.1
• new minor and major release may introduce database schema changes at any time and should generally not considered backwards compatible
• database schema changes are applied at startup of a new Quay version, once the update process passes this stage no rollbacks / downgrades can be done

On top of that, each minor version that we release should contain a hint that, if present, database schema changes will lead to backwards incompatibility.