Generally my rule of thumb is to keep the integrity checking as close to the data as possible. Usually that means integrating it into the schema/database (optio

Generally my rule of thumb is to keep the integrity checking as close to the data as possible. Usually that means integrating it into the schema/database (optionally with triggers), as long as that has proper tooling (versioning specifically). With more complex checks it might be necessary to build a periodically runnable check mechanism. At startup might be a good way to do it, or some sort of cronjob. I can imagine that in larger systems there might even be separate services to check data integrity across other services.