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Database / Supabase Intermediate to Advanced Interview Questions

What is the difference between JSONB and a fully normalized relational schema in Postgres?

A normalized schema splits data into separate tables connected by foreign keys, with each fact stored once; a JSONB column instead stores a whole nested document as a single value inside one row, queryable with operators like ->, ->>, and @>, and indexable with a GIN index.

Normalization enforces consistency through foreign keys and makes cross-entity queries (joins) efficient, but requires a schema change whenever the shape of the data changes. JSONB tolerates a flexible, evolving shape without a migration — useful for things like a form's arbitrary custom fields, third-party API payloads you don't fully control, or settings blobs — but it trades away foreign key enforcement and makes some queries (like aggregating across a specific nested field on a very large table) less efficient than an equivalent normalized column would be.

What does JSONB tolerate that a strictly normalized schema does not, without a migration?
What does normalization enforce that a JSONB blob does not?

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