Borrowing it
Nothing to install: this file belongs to irahardianto/rugged-gemini. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/irahardianto/rugged-gemini/main/.gemini/skills/database-design-principles/SKILL.mdgit clone --depth 1 https://github.com/irahardianto/rugged-geminiWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/irahardianto/rugged-gemini/database-design-principles)<a href="https://agentmods.dev/skills/irahardianto/rugged-gemini/database-design-principles"><img src="https://agentmods.dev/badge/skills/irahardianto/rugged-gemini/database-design-principles/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/irahardianto/rugged-gemini/database-design-principles"><img src="https://agentmods.dev/badge/skills/irahardianto/rugged-gemini/database-design-principles.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00028 | $0.00744 |
| Opus 5.5 | $0.00011 | $0.00298 |
| Sonnet 5.5 | $0.00006 | $0.00149 |
| Haiku 4.5 | $0.00003 | $0.00074 |
Grade A, and why
database-design-principles scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Database Design Principles
Schema
Normalization: start 3NF, denormalize only with measured perf need. One entity per table. No derived data unless explicit cache.
Naming: tables=plural snake_case (users, task_assignments). Columns=singular snake_case. FKs={table_singular}_id. Indexes=idx_{table}_{cols}. Constraints={type}_{table}_{cols}.
Required columns: id (bigint IDENTITY for single-DB, UUIDv7 for distributed — avoid random UUIDv4), created_at (timestamptz, immutable), updated_at (timestamptz, auto-update).
Data type selection: timestamptz over timestamp. text over varchar(n) unless constraint needed. numeric over float for money. bigint over int for IDs.
Migrations
Safety: never drop prod columns without deprecation. Never rename directly (add new → migrate → drop old). Always reversible (up + down). Test on prod data copy.
Strategy: 1. additive → 2. backfill → 3. update code → 4. drop old in future migration.
Queries
Design-level: ensure indexes cover query access patterns. Validate query plans during schema review. For SQL coding patterns (parameterized queries, SELECT hygiene, N+1 avoidance, timeouts), see @.gemini/skills/sql-idioms/SKILL.md.
Transactions: for multi-row/table ops. Choose appropriate isolation level. Never hold during user interaction or external calls. For locking patterns (deadlock prevention, advisory locks, SKIP LOCKED), see @.gemini/skills/sql-idioms/SKILL.md § Concurrency & Locking.
Partitioning
Tables >100M rows or time-series data → range partition by time. Enables instant partition drops vs slow DELETE.
Security at Schema Level
Row-Level Security: for multi-tenant data, enable RLS + FORCE to enforce database-level tenant isolation. Never rely solely on application-layer filtering. Index columns used in RLS policies.
Least privilege: create separate roles (readonly, writer) with specific table grants. Revoke default public access. Never use superuser for application queries.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 64 lines · 28 tokens per session scan A a8bbcdc3cff6
database-design-principles is a skill published in the GitHub repository irahardianto/rugged-gemini (5 stars, last pushed 5mo ago), licensed MIT. It adds 28 tokens to every session and 744 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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