You don’t need foreign keys, no. But you do need referential integrity and foreign keys implemented and enforced by the database is usually the easiest.
If you’re disciplined it’s not difficult to implement yourself in the application, but the challenge is if folks can access the database directly. If so, good luck, since it’s inevitable that they end up making modifications and break integrity.
If one insists on not having foreign keys (and there are decent reasons to not have them), I would really really suggest not allowing direct access to the database and enforce whatever application be the main or only client to the database.
If you’re disciplined it’s not difficult to implement yourself in the application, but the challenge is if folks can access the database directly. If so, good luck, since it’s inevitable that they end up making modifications and break integrity.
If one insists on not having foreign keys (and there are decent reasons to not have them), I would really really suggest not allowing direct access to the database and enforce whatever application be the main or only client to the database.