You rarely know everything before you have to start building. This is the workflow I use to build the parts that are settled, hold the parts that are not as defaulted decisions with known reversal costs, and never paint into a corner. Two anchors carry it: invariants made unrepresentable, and a decision register threaded through the code as a greppable ID.
You find an over-restriction because something legitimate breaks and points at the spot, and it breaks earlier the earlier you encode the rule. You do not find an over-permission the same way, because nothing legitimate ever exercises it. Here is the asymmetry, a worked example, and where it stops being true.
Database-managed binary JSON formats solve storage and query performance problems. JSONB enables fast PostgreSQL queries with indexing, while BSON adds extended types for MongoDB. Learn when databases beat text JSON.