Whether the shape of the system can carry what you plan to do next, and what would have to change if it cannot.
Schema, integrity, migrations and backups. The area where a mistake is least reversible and most often unnoticed.
A technical review of authentication, authorization, secrets and exposure. Not a compliance certificate, and never presented as one.
Where generated code concentrated, what has no tests, and what nobody on your side can explain.
Pick the level of involvement that fits, describe your product, and we begin there.