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:
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 — 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 — 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 — 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 Pydantic models from schema become the backend's data access contracts |
performance-profiler |
Index strategy recommendations are validated against real query execution plans |
Schema Designer proposes indexes, Performance Profiler confirms effectiveness with EXPLAIN ANALYZE data |
senior-secops |
RLS policies and column encryption align with security compliance requirements |
Security requirements flow in, RLS policies and encryption specifications flow out for audit verification |
observability-designer |
Audit log schema provides the foundation for operational dashboards and alerting |
Audit log table structure feeds into observability pipelines for change tracking and anomaly detection |
1---2name: database-schema-designer3description: 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.4license: MIT + Commons Clause5---6# Database Schema Designer
7
8Design 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.
9
10## Keywords
11
12database schema, schema design, normalization, migration, ERD, row-level security, indexing, multi-tenancy, soft deletes, audit trail, Drizzle, Prisma, PostgreSQL
13
14## Core Capabilities
15
16- **Schema design from requirements** — extract entities/relationships from natural language, apply 1NF–3NF normalization, add timestamps/soft-delete/audit/versioning, generate complete DDL.
17- **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.
18- **Index strategy** — composite, partial, covering, and GIN/GiST indexes mapped to query patterns; bloat detection and maintenance.
19- **Type generation** — TypeScript interfaces + Zod schemas and Python dataclasses + Pydantic models from the DB schema (enums as string unions).
20- **Security** — Row-Level Security for multi-tenant isolation, column-level PII encryption, audit logging with before/after JSON snapshots.
21
22## When to Use
23
24- Designing tables for a new feature
25- Reviewing an existing schema for normalization or performance issues
26- Adding multi-tenancy to a single-tenant schema
27- Planning a breaking schema migration
28- Generating ERD documentation for a service
29
30## Clarify First
31
32Before designing the schema, confirm these inputs. If any is unknown or vague, ASK — do not assume:
33
34- [ ] **Requirements or existing DDL** — the entities/relationships in natural language, or the schema to review (the source the design is derived from)
35- [ ] **Engine & ORM** — PostgreSQL/MySQL/SQLite and Drizzle/Prisma/TypeORM/Alembic (sets the migration and type-generation output format)
36- [ ] **Cross-cutting needs** — multi-tenancy/RLS, soft deletes, audit trails, or temporal data (determines which patterns and policies are generated)
37
38Stop 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.
39
40## Tools
41
42| Tool | Purpose | Command |
43|------|---------|---------|
44| `erd_generator.py` | Parse SQL DDL and generate a Mermaid ER diagram | `python scripts/erd_generator.py schema.sql -o erd.mmd` |
45| `migration_diffr.py` | Diff two SQL schemas into migration ALTER statements (with rollback) | `python scripts/migration_diffr.py old.sql new.sql` |
46| `schema_validator.py` | Validate DDL for normalization violations, missing indexes, naming | `python scripts/schema_validator.py schema.sql --strict` |
47
48## References
49
50Load the reference that matches the task — keep this file lean and pull detail on demand:
51
52- **[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.
53- **[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.
54- **[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.
55
56## Scope & Limitations
57
58**This skill covers:**
59- Relational schema design for PostgreSQL, MySQL, and SQLite including normalization through 3NF
60- Migration generation and zero-downtime migration planning for Drizzle, Prisma, TypeORM, and Alembic
61- Row-Level Security policies, index strategy, and type generation (TypeScript and Python)
62- Cross-cutting patterns: multi-tenancy, soft deletes, audit trails, optimistic locking, and temporal data
63
64**This skill does NOT cover:**
65- NoSQL or document database design (MongoDB, DynamoDB, Cassandra) — see `senior-data-engineer` for broader data store guidance
66- Query optimization and execution plan analysis beyond index recommendations — see `performance-profiler` for runtime profiling
67- Database infrastructure provisioning, replication, or failover configuration — see `senior-cloud-architect` for cloud database setup
68- Application-layer ORM patterns, connection pooling, or caching strategies — see `senior-backend` for backend architecture decisions
69
70## Integration Points
71
72| Skill | Integration | Data Flow |
73|-------|-------------|-----------|
74| `migration-architect` | Hands off generated DDL and migration files for sequencing across services | Schema Designer produces migrations, Migration Architect orchestrates cross-service rollout order |
75| `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 |
76| `senior-backend` | Generated types and ORM schemas plug into repository and service layers | TypeScript interfaces and Pydantic models from schema become the backend's data access contracts |
77| `performance-profiler` | Index strategy recommendations are validated against real query execution plans | Schema Designer proposes indexes, Performance Profiler confirms effectiveness with `EXPLAIN ANALYZE` data |
78| `senior-secops` | RLS policies and column encryption align with security compliance requirements | Security requirements flow in, RLS policies and encryption specifications flow out for audit verification |
79| `observability-designer` | Audit log schema provides the foundation for operational dashboards and alerting | Audit log table structure feeds into observability pipelines for change tracking and anomaly detection |
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