Database Migration Safety Check skill for Claude and Codex

Database Migration Safety Check as an AI skill. It asks for The migration, Database, Largest affected table and 3 more, then does the rest. Free to install in…

Install it once and Claude or Codex runs it for you. When your request matches, your AI loads the skill, asks for anything it is missing, and works through the template itself. Prefer to fill it in by hand? See the full prompt template.

Download the skill (.zip) · View SKILL.md

When it is used

Use when a schema migration is about to run on a live database and needs a check for locks, backfills, reversibility, and deploy order. Do not use for designing the schema itself or moving data between database engines. Related topics: data, devops.

What it will ask you for

• The migration (longer free text)
• Database (choose one: Postgres, MySQL, SQL Server, Other)
• Largest affected table (free text, e.g. "Name and approximate row count")
• Traffic (choose one: Constant, Business hours only, Low, Offline window available)
• Deploy style (choose one: Rolling, Blue and green, Stop and start)
• Rollback needed (choose one: Yes, No)

How it works

1. Read each statement and state the lock it takes and how long it will hold on the largest table.
2. Flag the risky operations, such as volatile defaults, not-null additions, type changes, and non-concurrent index builds.
3. Move large backfills out of the migration into batched jobs with pauses between batches.
4. Reorder the change into compatible steps so old and new application code both work at every moment of the rollout.
5. Write the down migration if required, naming steps that cannot be undone, and add a before and after checklist.

What you get

A statement-by-statement risk table, a safer rewritten migration sequence, and a before and after deploy checklist.

What it watches out for

• Testing the migration on a small dev table where the lock lasts milliseconds, then meeting a ten-minute lock in production.
• Dropping a column in the same release that stops using it, so a rolling deploy crashes the old instances.
• Running a huge backfill inside one transaction, which bloats the log and blocks vacuum.

How to install

Claude.ai and the Claude desktop app

1. Download the skill .zip.
2. Open Settings, then Capabilities, and find Skills.
3. Choose Upload skill and select the .zip.
4. Ask Claude for help with the task. It loads the skill when your request matches.

Claude Code

1. Download the skill .zip.
2. Unzip it into ~/.claude/skills/ (or .claude/skills/ inside a project).
3. Start a new session. Claude Code loads the skill when your request matches.

Codex

1. Download the skill .zip.
2. Unzip it into ~/.agents/skills/ (or .agents/skills/ inside a project).
3. Codex picks it up on its own. Type $ and the skill name to use it, or just ask for the task.

Cursor

1. Download the Cursor rule (.mdc).
2. Save it in .cursor/rules/ inside your project.
3. Cursor's agent applies the rule when your request matches its description.

AGENTS.md (Codex, Cursor, and other coding agents)

1. Copy the AGENTS.md section.
2. Paste it into AGENTS.md at the root of your repository, creating the file if needed.
3. Coding agents that read AGENTS.md follow it when your request fits.