Backend engineer / DBA

SQL query optimizer

Immediate result: A rewritten query, the indexes to add and how to verify the speed-up with EXPLAIN.

Problem it solvesA slow query is hurting the app and it isn't obvious whether the fix is an index, a rewrite or both.

Add this skill to

You paste

PostgreSQL: SELECT * FROM orders WHERE DATE(created_at) = '2026-10-01' — 4M rows, 3 s

You get

Bottleneck: DATE() on created_at prevents index use.

Rewrite: WHERE created_at >= '2026-10-01' AND created_at < '2026-10-02'

Index: CREATE INDEX ON orders (created_at); expect an Index Scan in EXPLAIN ANALYZE.

About this skill

About SQL query optimizer

A slow query can be an index problem, a query problem or both, and guessing wastes a day. This skill looks for the usual culprits — full table scans, functions wrapped around indexed columns, N+1 patterns, OR conditions and SELECT * — and rewrites the query so it returns identical results faster. It recommends specific indexes with the column order explained, gives the EXPLAIN command to run and tells you what a healthy plan looks like. It states its assumptions about your data and warns you if a rewrite could change row counts, so speed never costs correctness.

SQL query optimizer AI skill for Backend engineer / DBA: you paste "PostgreSQL: SELECT * FROM orders WHERE DATE(created_at) = '2026-10-01' — 4M rows, 3 s" and get "Bottleneck: DATE() on created_at prevents index use."
SQL query optimizer — example input and the first lines it returns. Works in ChatGPT, Claude and Gemini.
Job profile
Software engineering · Backend engineer / DBA
Works in
ChatGPT, Claude, Gemini, Copilot, Claude Code
Format
Agent Skills (SKILL.md)
Price
Free, no sign-up
Install instructions

Copy, paste, send

  1. Cold email writerCopy skillCopied ✓1 Copy the skillPress Copy skill.
  2. ANY AI ASSISTANTSKILLPaste here, then press Enter2 Paste it into a new chatChatGPT, Claude, Gemini or Copilot.
  3. ANY AI ASSISTANT3 Send your inputSend the slow SQL query.
The skill — paste this into your AI assistant
# Skill: SQL query optimizer

You are running the "SQL query optimizer" skill for me. I work as: Backend engineer / DBA. What I need from you: a rewritten query, the indexes to add and how to verify the speed-up with EXPLAIN.

## When I send you the slow SQL query, table definitions or column names, row counts if known and my database (PostgreSQL, MySQL, SQL Server)
1. Identify the likely bottleneck (full scans, N+1, functions on indexed columns, SELECT *, OR conditions).
2. Rewrite the query to return identical results faster.
3. Recommend specific indexes with column order explained.
4. Give the EXPLAIN command and what to look for in its output.

## Reply in this format
- Likely bottleneck
- Rewritten query
- Indexes to add (CREATE INDEX statements)
- Verify with EXPLAIN
- Trade-offs

## Rules
- State any assumption about data distribution.
- Never change results: call out if a rewrite could change row counts.
- Use only the facts I give you; mark anything you had to assume with [ASSUMPTION].
- If something essential is missing, ask me one short question, then continue.
- No preamble or filler: start with the result.

Confirm you're ready in one line, then wait for me to send the slow SQL query, table definitions or column names, row counts if known and my database (PostgreSQL, MySQL, SQL Server).

Then sendThe slow SQL query, table definitions or column names, row counts if known and your database (PostgreSQL, MySQL, SQL Server). For example: PostgreSQL: SELECT * FROM orders WHERE DATE(created_at) = '2026-10-01' — 4M rows, 3 s

ChatGPT

  1. Fastest: paste the skill as your first message in a new chat, then send your input.
  2. To keep it: open a Project, choose Instructions (or Settings → Personalization → Custom instructions for every chat) and paste it there.
  3. To share it with a team: create a custom GPT and paste the skill into its Instructions.
  4. In the Codex app: copy the skill's folder into ~/.codex/skills/ (or Customize → Skills → Add → Create skill).

Claude

  1. Fastest: paste the skill as your first message in a new chat, then send your input.
  2. To keep it: create a Project, open Project instructions and paste the skill.
  3. As a Claude Skill: download the skill's ZIP, then in Claude open Settings → Skills → Add → Upload skill and choose the file.

Gemini

  1. Fastest: paste the skill as your first message in a new chat, then send your input.
  2. To keep it: open Gems → New Gem, paste the skill into Instructions and save.

Microsoft Copilot

  1. Fastest: paste the skill as your first message, then send your input.
  2. In Microsoft 365 Copilot, save it as a prompt or paste it into an agent's instructions to reuse it.

Any other assistant

  1. Paste the skill as the system prompt or first message in any chat assistant (Perplexity, Meta AI, DeepSeek, Mistral, local models).
  2. Coding agents that read the Agent Skills format (SKILL.md) can load the downloaded file from their skills folder.

Install it permanently

Upload it to Claude, add it to ChatGPT's Codex app, clone it into Claude Code, or download the SKILL.md for any agent. Full guide with screenshots →

Download the ZIP and upload it in Claude. Claude then uses the skill on its own whenever a request matches.

Download ZIP

Quick setup

  1. In Claude, open Settings → Skills (under Customize).
  2. Click Add → Upload skill.
  3. Choose the ZIP — don't unzip it — and make sure the skill is switched on.
Claude Settings with Skills selected under Customize, and the Add menu open showing Upload skill, Create a skill, Create with Claude and Record your screen

Repositoryscienceofapps.com/skills/ai-skills.git · all 200 skills, one folder each, plain git over HTTPS

What it does

The steps it follows

  1. Identify the likely bottleneck (full scans, N+1, functions on indexed columns, SELECT *, OR conditions).
  2. Rewrite the query to return identical results faster.
  3. Recommend specific indexes with column order explained.
  4. Give the EXPLAIN command and what to look for in its output.
What you get back

The reply format

  • Likely bottleneck
  • Rewritten query
  • Indexes to add (CREATE INDEX statements)
  • Verify with EXPLAIN
  • Trade-offs

Rules it never breaks

  • State any assumption about data distribution.
  • Never change results: call out if a rewrite could change row counts.
  • Uses only the facts you give it and marks assumptions.
FAQs

Questions about SQL query optimizer

What does the SQL query optimizer skill do?

A slow query is hurting the app and it isn't obvious whether the fix is an index, a rewrite or both. The skill fixes that: a rewritten query, the indexes to add and how to verify the speed-up with EXPLAIN.

How do I install SQL query optimizer in ChatGPT, Claude or Gemini?

Copy the skill and paste it as the first message of a new chat, then send your input. To keep it, paste it into a ChatGPT Project or custom GPT, a Claude Project or a Gemini Gem, or upload the SKILL.md file as a Claude Skill.

What do I send SQL query optimizer after installing it?

Send the slow SQL query, table definitions or column names, row counts if known and your database (PostgreSQL, MySQL, SQL Server). If something essential is missing, the skill asks you one short question and then continues.

Is the SQL query optimizer skill free?

Yes. It's free to copy, use and adapt, with no sign-up, and works in the free versions of ChatGPT, Claude, Gemini and Copilot.

More for software engineering
Backend engineer / developer advocate

API docs writer

ProblemEndpoints ship without docs, so other teams ping you on Slack to ask how to call them.

You paste

Express: router.post('/v1/invoices', auth, validate(invoiceSchema), createInvoice)

You get

POST /v1/invoices — Create an invoice for a customer.

Auth: Bearer token (required).

Errors: 401 missing token · 422 validation failed (body lists fields).

Immediate resultReference docs for each endpoint: purpose, parameters, example request, example response and errors.

Software engineer

Commit message writer

ProblemCommit history full of 'fix stuff' makes it impossible to find when and why something changed.

You paste

diff: retry wrapper added around payment API call, timeout 3s → 10s

You get

fix(payments): retry gateway calls and raise timeout to 10s

Gateway p99 latency exceeds 3s at peak, causing false failures. Retries twice with backoff. Refs PAY-142.

Immediate resultA Conventional Commits message with a clear subject line and a body that explains why.

Tech lead

Refactor planner

ProblemA big refactor done in one go breaks things and stalls for weeks.

You paste

Split UserService (1,800 lines: auth, billing, notifications) into three services

You get

Step 1: add characterization tests for the 12 public methods (no code change).

Step 2: extract NotificationService behind the same interface; UserService delegates.

Step 3: move billing calls… each step ships alone.

Immediate resultA refactor broken into small, safe, independently shippable steps with a test at each step.

Free PDF · 74 pages · 2 editions

The Laws of UX, in one field guide

60 research-backed principles in 6 categories — what each one means, why it works on the human brain and how to use it on your own screens. Written by Sushant Singh, founder of Science of Apps, who has scaled consumer apps to lacs of users and spent 10+ years leading product across startups and digital businesses in the US, EU & India.

Pick your edition
Free. No card, no paywall — just your email.
Free PDF · 74 pages

Get Laws of UX by email

Choose your edition

You’ll also get occasional UX psychology tips. Unsubscribe anytime. Privacy policy

Free PDF · 90 pages · 2 editions

100+ Subscription Paywalls, decoded

110 real paywalls from top apps, taken apart, rated out of 5 and decoded with the Laws of UX — plus the frameworks, copy and checklists to ship your own. By Sushant Singh, founder of Science of Apps.

  • 110 paywalls rated
  • 34 Laws of UX
  • 12 frameworks

Which paywall scored 4.8 out of 5, and which scored 2.6? It’s all inside.

Pick your edition
Free. No card, no paywall — just your email.
Free PDF · 90 pages

Get 100+ Paywalls, Decoded by email

Choose your edition

You’ll also get occasional UX psychology tips. Unsubscribe anytime. Privacy policy