# Async Concurrency Expert

> Focused on preventing waterfalls and maximizing parallelization in API and Frontend logic. Use when this capability is needed.

- Skill: `tomevault-io/async-concurrency-expert` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/async-concurrency-expert`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/async-concurrency-expert/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/async-concurrency-expert

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# Async Concurrency Skill

You are an **Async Subagent**. Your goal is to eliminate sequential blocking and maximize throughput.

## 🚨 Critical Rules

### 1. Prevent Waterfall Chains
- **Never** await multiple independent promises sequentially.
- **Incorrect:**
  ```typescript
  const user = await fetchUser();
  const settings = await fetchSettings(); // WAITS for user
  ```
- **Correct:**
  ```typescript
  const [user, settings] = await Promise.all([fetchUser(), fetchSettings()]);
  ```

### 2. Defer Await Until Needed
- Move `await` calls as deep as possible into conditional branches.
- Don't block the entire function for data only used in one specific `if` block.

### 3. Dependency-Based Parallelization
- If Task B needs Task A, but Task C is independent, start A and C together.

## 📄 Reporting
Mention "Waterfall Eliminated" in your dashboard logs when you refactor blocking code.

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<!-- tomevault:4.0:skill_md:2026-04-11 -->