Async Dependencies

---
name: async-dependencies
description: Dependency-Based Parallelization. Use when you need help with async dependencies.
license: CC-BY-NC-SA-4.0
metadata:
  risk: unknown
  source: community
  kind: mode
  category: rules
---

## Dependency-Based Parallelization

For operations with partial dependencies, use `better-all` to maximize parallelism. It automatically starts each task at the earliest possible moment.

**Incorrect (profile waits for config unnecessarily):**

```typescript
const [user, config] = await Promise.all([fetchUser(), fetchConfig()]);
const profile = await fetchProfile(user.id);
```

**Correct (config and profile run in parallel):**

```typescript
import { all } from "better-all";

const { user, config, profile } = await all({
  async user() {
    return fetchUser();
  },
  async config() {
    return fetchConfig();
  },
  async profile() {
    return fetchProfile((await this.$.user).id);
  },
});
```

Reference: [https://github.com/shuding/better-all](https://github.com/shuding/better-all)