Database Schema Designer

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

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Audit 0.4.1 · source sha 6e3fcbdbb5cf · 19 Oct 2026Report an issue or request a re-scan

• Publisherborghei GitHub userOwner of the repository this skill is read from
• Source folderborghei/Claude-Skills/engineering/database-schema-designerThe exact folder we audited
• LicenceNOASSERTIONAs the repository states it
• Commit pinned for this verdict6e3fcbdbb5cfA new audit runs when the source changes
• Repository statusNot archivedLast push 12 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Design relational schemas from requirements with normalization, migrations, ERDs, RLS policies, and indexes for PostgreSQL, MySQL, and SQLite. Use when designing new features, reviewing schemas, or adding multi-tenancy.

---
name: database-schema-designer
description: >
  Design relational schemas from requirements with normalization, migrations, ERDs, RLS
  policies, and indexes for PostgreSQL, MySQL, and SQLite. Use when designing new features,
  reviewing schemas, or adding multi-tenancy.
license: MIT + Commons Clause
metadata:
  version: 1.1.0
  author: borghei
  category: engineering
  domain: data-architecture
  tier: POWERFUL
  updated: 2026-06-17
  frameworks: drizzle, prisma, alembic, typeorm
---
# Database Schema Designer

Design normalized relational database schemas from requirements and generate migrations, TypeScript/Python types, seed data, Row-Level Security policies, index strategies, and ERD diagrams. Handles multi-tenancy, soft deletes, audit trails, optimistic locking, polymorphic associations, and temporal data patterns. Supports PostgreSQL, MySQL, and SQLite with Drizzle, Prisma, TypeORM, and Alembic.

## Keywords

database schema, schema design, normalization, migration, ERD, row-level security, indexing, multi-tenancy, soft deletes, audit trail, Drizzle, Prisma, PostgreSQL

## Core Capabilities

- **Schema design from requirements** — extract entities/relationships from natural language, apply 1NF–3NF normalization, add timestamps/soft-delete/audit/versioning, generate complete DDL.
- **Migration planning** — forward and rollback migrations, zero-downtime patterns for large tables, column additions/type changes/backfills across Drizzle, Prisma, TypeORM, Alembic, and raw SQL.
- **Index strategy** — composite, partial, covering, and GIN/GiST indexes mapped to query patterns; bloat detection and maintenance.
- **Type generation** — TypeScript interfaces + Zod schemas and Python dataclasses + Pydantic models from the DB schema (enums as string unions).
- **Security** — Row-Level Security for multi-tenant isolation, column-level PII encryption, audit logging with before/after JSON snapshots.

## When to Use

- Designing tables for a new feature
- Reviewing an existing schema for normalization or performance issues
- Adding multi-tenancy to a single-tenant schema
- Planning a breaking schema migration
- Generating ERD documentation for a service

## Clarify First

Before designing the schema, confirm these inputs. If any is unknown or vague, ASK — do not assume:

- [ ] **Requirements or existing DDL** — the entities/relationships in natural language, or the schema to review (the source the design is derived from)
- [ ] **Engine & ORM** — PostgreSQL/MySQL/SQLite and Drizzle/Prisma/TypeORM/Alembic (sets the migration and type-generation output format)
- [ ] **Cross-cutting needs** — multi-tenancy/RLS, soft deletes, audit trails, or temporal data (determines which patterns and policies are generated)

Stop rule: ask only the 2-3 that most change the output. If the user says "just draft it," proceed and list your assumptions at the top of the artifact.

## Tools

| Tool | Purpose | Command |
|------|---------|---------|
| `erd_generator.py` | Parse SQL DDL and generate a Mermaid ER diagram | `python scripts/erd_generator.py schema.sql -o erd.mmd` |
| `migration_diffr.py` | Diff two SQL schemas into migration ALTER statements (with rollback) | `python scripts/migration_diffr.py old.sql new.sql` |
| `schema_validator.py` | Validate DDL for normalization violations, missing indexes, naming | `python scripts/schema_validator.py schema.sql --strict` |

## References

Load the reference that matches the task — keep this file lean and pull detail on demand:

- **[references/schema-design-and-security.md](references/schema-design-and-security.md)** — the 4-step requirements-to-schema process, the full Drizzle ORM schema example, cross-cutting concerns, and PostgreSQL Row-Level Security policies. Read when designing a new schema or adding multi-tenancy.
- **[references/indexes-and-migrations.md](references/indexes-and-migrations.md)** — the index-type decision framework, index anti-patterns, zero-downtime migration patterns (add NOT NULL column, rename column), and Mermaid ERD generation. Read when choosing indexes or planning a safe migration.
- **[references/best-practices-and-troubleshooting.md](references/best-practices-and-troubleshooting.md)** — common pitfalls, best practices, the troubleshooting table, and the success-criteria bar. Read before shipping a schema or when diagnosing a problem.

## Scope & Limitations

**This skill covers:**
- Relational schema design for PostgreSQL, MySQL, and SQLite including normalization through 3NF
- Migration generation and zero-downtime migration planning for Drizzle, Prisma, TypeORM, and Alembic
- Row-Level Security policies, index strategy, and type generation (TypeScript and Python)
- Cross-cutting patterns: multi-tenancy, soft deletes, audit trails, optimistic locking, and temporal data

**This skill does NOT cover:**
- NoSQL or document database design (MongoDB, DynamoDB, Cassandra) — see `senior-data-engineer` for broader data store guidance
- Query optimization and execution plan analysis beyond index recommendations — see `performance-profiler` for runtime profiling
- Database infrastructure provisioning, replication, or failover configuration — see `senior-cloud-architect` for cloud database setup
- Application-layer ORM patterns, connection pooling, or caching strategies — see `senior-backend` for backend architecture decisions

## Integration Points

| Skill | Integration | Data Flow |
|-------|-------------|-----------|
| `migration-architect` | Hands off generated DDL and migration files for sequencing across services | Schema Designer produces migrations, Migration Architect orchestrates cross-service rollout order |
| `api-design-reviewer` | Schema entities map directly to API resource models and endpoint structure | Schema entities and relationships feed into REST/GraphQL resource definitions and validation rules |
| `senior-backend` | Generated types and ORM schemas plug into repository and service layers | TypeScript interfaces and Pydan

Excerpt, first 6,000 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/borghei/Claude-Skills
git -C Claude-Skills checkout 6e3fcbdbb5cf

Works in

1. 2026-10-19
   !CAUTION B 89 / 100

   first audit · source 6e3fcbdbb5cf

Questions about Database Schema Designer

• github.com/borghei/Claude-Skills/tree/main/engineering/database- — the audited source at commit 6e3fcbdbb5cf and every finding aboveObserved · 19 Oct 2026

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