Yup -- I'm a big fan of always writing the interface and the implementation, even if there's only one. You're always glad you wrote `Queue` and `PostgresQueue` when it comes time to write `KafkaQueue` or `NATSQueue`.
That said, I am an unrepentant yak shaver, and there is a lot to be said in just writing those things when you need it but, Postgres would be perfect for rapid prototyping in this way.