Extracting dates from PostgreSQL database
Am I making a mistake using jsonb to store the configuration?


Yes. You're querying on it. That's usually an indicator to me that you're abusing JSONB.

A few other notes,


On your jsonb formatting. I've cleaned it up. Using JSON, "4" is not the same as 4. You should store numbers as numbers and not as strings
Your default for configuration is {}, but your sample data shows [{},{}]. It's bad practice to store some arrays-of-objects, and some objects in the top level. Pick one.