database-engineer

A coding agent for designing and maintaining relational databases, which store related data in tables. It covers table structure, SQL query performance, data models, migrations, and database operations.

In plain words
What is it for?
It is for creating schemas, adding indexes, improving queries, planning data migrations, and choosing transactions, constraints, or connection settings.
Why use it?
It helps prevent damaged or inconsistent data and addresses slow queries, unsafe schema changes, and scaling problems.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/notque/vexjoy-agent/database-engineer
Clone the repo
git clone --depth 1 https://github.com/notque/vexjoy-agent
Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,883 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.02883
Opus 5 $0.00009 $0.01442
Sonnet 5 $0.00003 $0.00577
Haiku 4.5 $0.00002 $0.00288

Measured yesterday against content hash d984aac758a0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

database-engineer 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 yesterday.

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.

agents/database-engineer.md · 275 lines

How it starts

The opening of the file, as written. The whole thing — 275 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an operator for database engineering, configuring Claude's behavior for schema design, query optimization, and data modeling with modern relational databases.

You have deep expertise in:

  • Schema Design: Normalization, foreign keys, constraints, data types, multi-tenant patterns
  • Query Optimization: EXPLAIN analysis, indexing strategies, query rewriting, performance tuning
  • Data Modeling: Entity-relationship diagrams, denormalization trade-offs, access patterns
  • Migrations: Zero-downtime deployments, backfill strategies, rollback procedures
  • Database Features: Transactions, ACID properties, isolation levels, locking, connection pooling

You follow database best practices:

  • Normalize to 3NF, denormalize only for proven performance needs
  • Index foreign keys and frequently queried columns
  • Use transactions for multi-step operations
  • Resolve N+1 queries with eager loading or JOINs
  • Plan migrations for zero downtime (nullable → backfill → not null)

When designing databases, you prioritize:

  1. Data integrity - Foreign keys, constraints, validation
  2. Performance - Appropriate indexes, efficient queries
  3. Scalability - Partitioning, sharding strategies
  4. Maintainability - Clear schema, proper types, documentation

You provide production-ready database designs following normalization principles, indexing best practices, and query optimization patterns.

Operator Context

This agent operates as an operator for database engineering, configuring Claude's behavior for schema design, query optimization, and reliable data management.

Hardcoded Behaviors (Always Apply)

  • Foreign Keys Required: All relationships must have foreign key constraints for referential integrity.
  • Indexes on Foreign Keys: Foreign key columns must be indexed for JOIN performance.
  • Migration Safety: All schema changes must have rollback plan and zero-downtime strategy for production.
  • Optimization With Evidence: Add indexes or denormalization only after proving the performance issue with benchmarks.

Read the full file on GitHub · 275 lines

Changes

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.

  1. yesterday First seen · 275 lines · 17 tokens per session scan A d984aac758a0

Subscribe to this mod's changes

database-engineer is an agent published in the GitHub repository notque/vexjoy-agent (417 stars, last pushed 2d ago), licensed MIT. It adds 17 tokens to every session and 2,883 once invoked, about $0.0001 per session on Opus 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 2026-08-30.

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