[Databricks on AWS #0] The Target Architecture: Isolating Prod, Dev, and Sandbox with Unity Catalog

📚 Series: Databricks on AWS (Part 0, prologue) The Target Architecture ← you are here Building a Databricks AI Platform on AWS RBAC with Function-Role Groups Compute Governance: Pools, Policies, Clusters The BOOTSTRAP_TIMEOUT Mystery Fixing It with AWS PrivateLink How We Structure the Terraform Before the build story, here's the destination. This is the target-state data architecture we designed the whole platform toward — the three principles that shaped every later decision, and the Unity Catalog governance model that keeps production data safe from human hands. The rest of this series is a build log: workspaces, RBAC, compute, the networking rabbit hole, the Terraform layout. But every one of those decisions was made in service of a target picture we drew first . This post is that picture — the "to-be" architecture, not the scaffolding we happened to have up on any given week. It's built on three things Databricks basically hands you if you lean into them: the Lakehouse (one store, ACID tables, no separate warehouse to sync), the Medallion architecture (raw → cleaned → integrated → business, each layer a promotion), and Unity Catalog as the single governance plane across all of it. The interesting part isn't reciting those three buzzwords — it's the specific way we wire them so that prod, dev, and analyst sandboxes never step on each other. Three principles, and everything follows Almost every concrete rule later in this series is a consequence of one of these three. 1. Nobody touches production by hand. Create, update, delete in prod data happens only through an automated, code-reviewed pipeline running as a service principal. Human accounts don't get write on prod — not analysts, not engineers, not admins. The blast radius of a bad afternoon is capped at whatever a person can do with read-only. This one principle is why the whole "promote" flow later exists. 2. Never copy production to look at it. If an analyst wants to explore the gold layer, they read it in p