performance

性能技能

性能目标

前端（Web Vitals）： LCP < 2.5s，FID < 100ms，CLS < 0.1，FCP < 1.8s，TTFB < 600ms 后端： 响应时间 < 500ms（p95），冷启动 < 2s，错误率 < 1% 数据库： 查询时间 < 100ms，缓存命中率 > 80%

衡量性能

# Lighthouse audit
npx lighthouse https://motormetrics.app --view

# Bundle analysis
cd apps/web && ANALYZE=true pnpm build

# Load test with k6
k6 run --vus 100 --duration 5m load-test.js

优化包体积

动态导入

// ❌ Static import (loads immediately)
import { HeavyComponent } from "./heavy-component";

// ✅ Dynamic import (lazy load)
import dynamic from "next/dynamic";
const HeavyComponent = dynamic(() => import("./heavy-component"), {
  loading: () => <div>Loading...</div>,
  ssr: false,
});

Tree Shaking

// ❌ Imports entire library
import _ from "lodash";

// ✅ Import only what you need
import uniq from "lodash/uniq";

React 性能

避免重复渲染

// useMemo for expensive calculations
const processed = useMemo(() => expensiveOperation(data), [data]);

// useCallback for stable function references
const handleClick = useCallback(() => doSomething(), []);

// React.memo for pure components
const Child = React.memo(function Child({ name }) {
  return <div>{name}</div>;
});

对长列表进行虚拟化

import { FixedSizeList } from "react-window";

<FixedSizeList height={600} itemCount={items.length} itemSize={100} width="100%">
  {({ index, style }) => <Item style={style} data={items[index]} />}
</FixedSizeList>

数据库查询优化

添加索引

// packages/database/src/schema/cars.ts
export const cars = pgTable("cars", {
  make: text("make").notNull(),
  month: text("month").notNull(),
}, (table) => ({
  makeIdx: index("cars_make_idx").on(table.make),
}));

避免 N+1 查询

// ❌ N+1 queries
for (const post of posts) {
  post.author = await db.query.users.findFirst({ where: eq(users.id, post.authorId) });
}

// ✅ Single query with relation
const posts = await db.query.posts.findMany({ with: { author: true } });

仅选择所需列

// ❌ Selects all columns
const users = await db.query.users.findMany();

// ✅ Select specific columns
const users = await db.select({ id: users.id, name: users.name }).from(users);

使用分页

const cars = await db.query.cars.findMany({
  limit: 20,
  offset: (page - 1) * 20,
});

缓存

Redis 缓存

import { redis } from "@motormetrics/utils/redis";

export async function getCarsWithCache(make: string) {
  const cacheKey = `cars:${make}`;
  const cached = await redis.get(cacheKey);
  if (cached) return JSON.parse(cached as string);

  const cars = await db.query.cars.findMany({ where: eq(cars.make, make) });
  await redis.set(cacheKey, JSON.stringify(cars), { ex: 3600 });
  return cars;
}

Next.js 缓存

// Revalidate every hour
export const revalidate = 3600;

// Or use fetch with caching
const data = await fetch(url, { next: { revalidate: 3600 } });

图像优化

import Image from "next/image";

// ✅ Optimized image with priority for above-fold
<Image
  src="/hero.jpg"
  alt="Hero"
  fill
  sizes="(max-width: 768px) 100vw, 50vw"
  priority
/>

Vercel 函数优化

// API route with optimized config
export const config = {
  maxDuration: 60, // seconds
};

// Use edge functions for low-latency endpoints
export const runtime = "edge";

性能分析

性能中间件

// apps/api/src/middleware/performance.ts
export const performanceMiddleware = async (c: Context, next: Next) => {
  const start = performance.now();
  await next();
  const duration = performance.now() - start;

  c.header("X-Response-Time", `${Math.round(duration)}ms`);

  if (duration > 1000) {
    log.warn("Slow request", { path: c.req.path, duration: Math.round(duration) });
  }
};

查询分析

const start = performance.now();
const result = await db.query.cars.findMany();
const duration = performance.now() - start;

if (duration > 100) {
  console.warn(`Slow query: ${duration}ms`);
}

Vercel Analytics

在 Vercel Dashboard → Analytics 中查看：

• 函数执行时间
• 边缘响应时间
• Web Vitals 指标
• 请求量和错误

负载测试

// load-test.js (k6)
import http from "k6/http";
import { check } from "k6";

export const options = {
  stages: [
    { duration: "2m", target: 100 },
    { duration: "5m", target: 100 },
    { duration: "2m", target: 0 },
  ],
  thresholds: {
    http_req_duration: ["p(95)<500"],
    http_req_failed: ["rate<0.01"],
  },
};

export default function() {
  const res = http.get("https://api.motormetrics.app/api/v1/cars/makes");
  check(res, { "status 200": (r) => r.status === 200 });
}

性能检查清单

• 包体积 < 200KB（初始加载）
• LCP < 2.5s，FID < 100ms，CLS < 0.1
• API 响应 < 500ms
• 数据库查询 < 100ms
• 图像已优化（WebP/AVIF）
• 已实现代码拆分
• 已制定缓存策略
• 长列表已进行虚拟化
• 已启用压缩

快速优化项

1. 压缩：启用 gzip/brotli（体积减少 60-80%）
2. 图像优化：使用 Next.js Image 组件
3. 缓存：在 Redis 中缓存开销较大的操作
4. 索引：为频繁查询的列添加索引
5. 代码拆分：延迟加载大型组件
6. 记忆化：对开销较大的操作使用 useMemo/useCallback

参考资料

• Web Vitals：https://web.dev/vitals
• Next.js 性能：https://nextjs.org/docs/app/building-your-application/optimizing
• k6 负载测试：https://k6.io/docs