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Agent skill

Performance Fundamentals

by DanielPodolsky in DanielPodolsky/ownyourcode

Reviews performance including N+1 queries, re-renders, scalability.

MITAuto-check passedBackend & APIs

Install Performance Fundamentals

skills CLI
$ npx skills add DanielPodolsky/ownyourcode --skill performance-fundamentals -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install DanielPodolsky/ownyourcode performance-fundamentals --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/DanielPodolsky/ownyourcode.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/fundamentals/performance .claude/skills/performance-fundamentals && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
performance-fundamentals
GitHub stars
290
Used in
1 other repo
Token cost
~1.3k tokens
SKILL.md length
433 words
Files
1
Skills in repo
19
Repo updated
First seen
Licence
MIT

At a glance

Reviews performance including N+1 queries, re-renders, scalability.

  • Works in 5 steps: The N+1 Query Problem → Unnecessary Re-renders → Computing in Render → …
  • Junior asks is this performant
  • SKILL.md covers When to Apply, Review Checklist, Common Mistakes (Anti-Patterns) and Socratic Questions, plus 4 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Performance Fundamentals is an agent skill from DanielPodolsky/ownyourcode. Reviews performance including N+1 queries, re-renders, scalability. Use when junior asks "is this performant", "will this scale", "too slow", or builds loops, large lists, pagination, caching.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Backend & APIs, covering Caching. The repository describes itself as: Claude Code workflow for AI-mentored development. Work efficiently with Spec-Driven Development and the 6 Gates. Built to fight cognitive offloading — for developers using AI to… The licence is MIT.

When your agent uses it

  • Junior asks is this performant
  • Will this scale

Example prompts

  • “is this performant”
  • “will this scale”
  • “too slow”
  • “/performance-fundamentals”

Workflow steps

5 steps, taken from the step headings in SKILL.md.

  1. The N+1 Query Problem
  2. Unnecessary Re-renders
  3. Computing in Render
  4. Fetching Everything
  5. Missing Cleanup

What it can do on your machine

Read from SKILL.md and the folder at commit bd1f17c. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Performance Fundamentals loads about 1.3k tokens when it runs. Until then it costs about 54 tokens; SKILL.md has 433 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~54
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from DanielPodolsky/ownyourcode at commit bd1f17c, republished under its MIT licence (© DanielPodolsky). 433 words, ~1,285 tokens.

Download SKILL.mdSave it as .claude/skills/performance-fundamentals/SKILL.md (or your agent's skills folder).
name
performance-fundamentals
description
Reviews performance including N+1 queries, re-renders, scalability. Use when junior asks "is this performant", "will this scale", "too slow", or builds loops, large lists, pagination, caching.

Performance Fundamentals Review

"Premature optimization is the root of all evil, but mature ignorance is worse."

When to Apply

Activate this skill when reviewing:

  • Database queries (especially in loops)
  • React/Vue render logic
  • API response payloads
  • Data transformations
  • File operations
  • Caching decisions

Review Checklist

Database Performance
  • No N+1 queries: Are related records fetched in bulk, not loops?
  • Indexes: Are frequently queried fields indexed?
  • Pagination: Do list endpoints paginate results?
  • Select only needed fields: Are we fetching entire records unnecessarily?
Frontend Performance
  • Memoization: Are expensive computations cached?
  • Re-render prevention: Will state changes cause unnecessary re-renders?
  • Bundle size: Are heavy libraries lazy-loaded?
  • Image optimization: Are images properly sized and formatted?
API Performance
  • Response size: Is the payload minimal?
  • Compression: Is gzip/brotli enabled?
  • Caching headers: Are cacheable responses marked?
  • Async processing: Are slow operations queued?
Memory & Resources
  • Cleanup: Are subscriptions/timers cleaned up?
  • Memory leaks: Are event listeners removed?
  • Connection pooling: Are DB connections reused?

Common Mistakes (Anti-Patterns)

1. The N+1 Query Problem
❌ const users = await User.findAll();
   for (const user of users) {
     user.posts = await Post.findByUserId(user.id); // N queries!
   }

✅ const users = await User.findAll({
     include: [{ model: Post }] // 1 query with JOIN
   });
2. Unnecessary Re-renders
❌ function Parent() {
     const handleClick = () => {}; // New function every render
     return <Child onClick={handleClick} />;
   }

✅ function Parent() {
     const handleClick = useCallback(() => {}, []);
     return <Child onClick={handleClick} />;
   }
3. Computing in Render
❌ function UserList({ users }) {
     // Runs on every render
     const sorted = users.sort((a, b) => a.name.localeCompare(b.name));
     return <ul>{sorted.map(...)}</ul>;
   }

✅ function UserList({ users }) {
     const sorted = useMemo(
       () => [...users].sort((a, b) => a.name.localeCompare(b.name)),
       [users]
     );
     return <ul>{sorted.map(...)}</ul>;
   }
4. Fetching Everything
❌ GET /api/users → returns 10,000 users with all fields

✅ GET /api/users?page=1&limit=20&fields=id,name,email
5. Missing Cleanup
❌ useEffect(() => {
     const interval = setInterval(fetchData, 5000);
     // No cleanup! Runs forever.
   }, []);

✅ useEffect(() => {
     const interval = setInterval(fetchData, 5000);
     return () => clearInterval(interval);
   }, []);

Socratic Questions

Ask the junior these questions instead of giving answers:

  1. Scale: "What happens when there are 10,000 items? 1,000,000?"
  2. Queries: "How many database queries does this operation make?"
  3. Re-renders: "When this state changes, what components re-render?"
  4. Memory: "Is anything holding a reference after it's no longer needed?"
  5. Payload: "Does the client need ALL of this data?"

Big O Quick Reference

PatternComplexityExampleAt 10,000 items
Direct lookupO(1)map.get(key)1 op
Single loopO(n)array.find()10,000 ops
Nested loopsO(n²)for i { for j }100,000,000 ops
SortO(n log n)array.sort()~130,000 ops
Show full SKILL.md (162 more words)Show less

Performance Targets

MetricTargetMeasure With
Time to First Byte (TTFB)< 600msDevTools Network
Largest Contentful Paint (LCP)< 2.5sLighthouse
First Input Delay (FID)< 100msLighthouse
Cumulative Layout Shift (CLS)< 0.1Lighthouse
API Response Time< 200ms (p95)Server metrics

Red Flags to Call Out

FlagQuestion to Ask
Query inside a loop"Can we batch this into one query?"
No pagination"What if there are 100,000 records?"
SELECT *"Do we need all these fields?"
Large JSON in localStorage"Will this slow down page load?"
Inline function in JSX"Does this create a new function every render?"
setInterval without cleanup"What clears this when the component unmounts?"
Synchronous file operations"Should this be async?"
No loading states"What does the user see while waiting?"

Quick Wins

  1. Add indexes to frequently queried DB columns
  2. Paginate all list endpoints
  3. Lazy load below-the-fold content
  4. Compress API responses
  5. Cache expensive computations with useMemo
  6. Debounce search inputs
  7. Virtualize long lists (react-window)

© DanielPodolsky, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/fundamentals/performance of DanielPodolsky/ownyourcode.

Open the folder on GitHubat commit bd1f17c

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in DanielPodolsky/ownyourcode, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Performance Fundamentals next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Performance Fundamentals compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Performance Fundamentals this skillDanielPodolsky/ownyourcode2901 repos~1.3kAutomated safety check: PassMIT
Stripe Projectsfossasia/eventyay1.7k5 repos~2kAutomated safety check: NotesApache-2.0
FoundatioFoundatioFx/Foundatio2.1k—~3.9kAutomated safety check: PassApache-2.0
Wp Block Themesgambitph/Stackable3513 repos~985Automated safety check: PassGPL-3.0
Wp Performancegambitph/Stackable3513 repos~1.5kAutomated safety check: PassGPL-3.0
Effect Portable Patternsmillionco/expect3.6k—~3.7kAutomated safety check: PassCustom licence

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  • Backend Fundamentals

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  • Database Fundamentals

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    Reviews schema design, SQL queries, ORM patterns. An agent skill from DanielPodolsky/ownyourcode.

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  • Documentation Fundamentals

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  • Error Handling Fundamentals

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    Guides error handling for async operations and API calls. An agent skill from DanielPodolsky/ownyourcode.

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  • Frontend Fundamentals

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Categories

Questions about Performance Fundamentals

What does Performance Fundamentals do?

Reviews performance including N+1 queries, re-renders, scalability. Performance Fundamentals is an agent skill from DanielPodolsky/ownyourcode. Reviews performance including N+1 queries, re-renders, scalability.

When should I use Performance Fundamentals?

Performance Fundamentals fits situations like: junior asks is this performant; will this scale.

How do I install Performance Fundamentals in Claude Code?

Run `npx skills add DanielPodolsky/ownyourcode --skill performance-fundamentals -a claude-code`. Or copy the skill folder (.claude/skills/fundamentals/performance in DanielPodolsky/ownyourcode) into .claude/skills/performance-fundamentals in your project. Claude Code loads it when a task matches its description.

How do I install Performance Fundamentals in Codex?

Run `npx skills add DanielPodolsky/ownyourcode --skill performance-fundamentals -a codex`. Or copy the skill folder (.claude/skills/fundamentals/performance in DanielPodolsky/ownyourcode) into .agents/skills/performance-fundamentals in your project. Codex loads it when a task matches its description.

Can I use Performance Fundamentals in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add DanielPodolsky/ownyourcode --skill performance-fundamentals -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/performance-fundamentals, .gemini/skills/performance-fundamentals, .github/skills/performance-fundamentals and .opencode/skills/performance-fundamentals in your project.

What does Performance Fundamentals need to run?

SKILL.md names no scripts, command-line tools or credentials: Performance Fundamentals is instructions for the agent only.

Does Performance Fundamentals access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Performance Fundamentals safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Performance Fundamentals use?

Performance Fundamentals is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Performance Fundamentals use?

About 1.3k tokens (SKILL.md is roughly 5.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Performance Fundamentals?

Skills that share tags, products or a category with Performance Fundamentals: Stripe Projects (fossasia/eventyay, 1.7k stars), Foundatio (FoundatioFx/Foundatio, 2.1k stars), Wp Block Themes (gambitph/Stackable, 351 stars) and Wp Performance (gambitph/Stackable, 351 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Performance Fundamentals?

DanielPodolsky (a GitHub user) maintains it in DanielPodolsky/ownyourcode, which has 290 GitHub stars. The repository holds 19 skills in this directory. The repository was last updated on June 27, 2026.

Source: DanielPodolsky/ownyourcode on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.