Node.js Serverless Cold Starts Are Killing Your API Performance

Moving our SaaS API from Node.js + Express + Prisma to this stack wasn't smooth, but the results were worth it. AWS bills went way down, cold starts went from fucking forever to actually usable. Not sure on exact numbers but it's night and day. Here's the real story, including the bullshit they don't warn you about.

Yeah, the benchmarks aren't bullshit for once - Bun actually delivers about 4x the HTTP throughput vs Node.js.

Bun: Fast as Hell But Documentation Sucks

Latest Bun is legitimately fast - our API response times dropped way down. The recent releases bring way better Node.js compatibility and built-in S3 support. But getting there was a nightmare. The official documentation is sparse, and Stack Overflow has barely any Bun questions compared to Node.js.

The real-world testing actually backs this up - rare for benchmark articles to not be complete bullshit. Bun pushes like 50k+ req/sec or something, way better than Node.js.

What Actually Breaks:

• sharp package completely shits the bed - use @squoosh/lib instead
• bcrypt doesn't compile - switch to argon2
• Hot reload randomly stops working and you have to restart everything
• Some npm packages just refuse to install (looking at you, node-canvas)

What Actually Works:

• TypeScript runs without any build step bullshit
• Bundles shrink like crazy, probably cut them in half
• Cold starts on Lambda went from 2.5s to 400ms consistently
• Single binary deployment is stupidly simple

The package ecosystem is tiny. I keep a compatibility list of what works and what doesn't because honestly, the official tracking is about as reliable as a chocolate teapot. The Bun compatibility tracker is community-maintained and way more reliable than the official docs - it's maintained by people who actually use this stuff and it's way more accurate about what's broken.

Hono: Actually Good But Missing Ecosystem

Hono's documentation is actually well-written, unlike most JavaScript frameworks. Version 4 (released February 2024) added static site generation and client components, but for API work, the middleware system makes sense and TypeScript integration doesn't fight you every step of the way. The Hono GitHub repository shows active development with daily commits.

Production Reality Check:

• Deployed identically to Cloudflare Workers and AWS Lambda without code changes
• Our bundle shrunk like crazy, was some huge Express mess before
• Built-in Zod validation caught schema errors that would've hit production
• OpenAPI generation actually works (looking at you, Swagger/Express setup)

Pain Points Nobody Mentions:

• Ecosystem is minuscule - forget finding random middleware packages
• Error messages are sometimes cryptic compared to Express
• Authentication middleware choices are limited (we built our own JWT handler)
• Community is small, so debugging weird issues means reading source code

The edge compatibility is real though. Same codebase runs on Cloudflare Workers for our public API and AWS Lambda for admin functions.

Drizzle: Prisma Withdrawal Was Painful But Worth It

Switching from Prisma to Drizzle took our team 3 weeks and a lot of swearing. But now I can actually see the SQL queries and optimize them when things go wrong. The bundle size comparison is brutal - Drizzle's about 1.5MB while Prisma clocks in at 6.5MB.

Migration Hell:

• No automatic migration tool from Prisma schemas
• I manually rewrote like 40 models, took forever
• Learning SQL again after years of Prisma magic
• Generated TypeScript types look different, broke some frontend code

Production Wins:

• Bundle size dropped massively (confirmed by migration studies)
• Can actually debug slow queries by reading the generated SQL
• Connection pooling works predictably (Prisma's pooling was a black box)
• Type inference is legitimately better - schema changes break at compile time
• Performance benchmarks show Drizzle is consistently faster at runtime

The Real Trade-off:
Prisma is magic until it breaks, then you're fucked. Drizzle makes you write actual SQL, which is annoying until you need to debug something at 3am. I prefer seeing the SQL.

Integration Gotchas That Will Bite You

Docker Deployment:
Spent an entire Saturday debugging weird SSL cert issues with Alpine. Turns out Bun doesn't play nice with Alpine's SSL setup - something about certificate chain validation failing in random production requests. Switched to Ubuntu base images and it just worked. No idea why the SSL implementation is different, but I'm not going back to find out. Our production Docker images still shrunk way down compared to the Node.js mess.

Database Connections:
Lambda + Drizzle = use single connections (max: 1). Learned this after 2 days of getting random "connection terminated unexpectedly" errors. Turns out when Lambda containers freeze, connection pools don't handle the resume gracefully. I was getting ECONNRESET errors on like 30% of requests after periods of inactivity. Single connections just reconnect automatically when the container wakes up.

Package.json Nightmares:
Bunch of npm packages are fucked. Keep a Node.js environment around for testing packages before committing to them. Recent security fixes show the ecosystem is still maturing.

TypeScript Compilation:
Bun's TypeScript support isn't 100% compatible with tsc. Some advanced type gymnastics break. We had to simplify some utility types.

This stack is fast and the developer experience is good once you get through the initial pain. But don't expect a smooth migration - budget 2-3 weeks for a medium-sized API and keep your Node.js deployment ready as backup.

The question is: how do you actually implement this thing without losing your sanity? That's what we'll cover next.

Let me walk you through setting this up from scratch. I'll include all the fucking around you'll actually have to do, not the sanitized version that assumes everything works on the first try.

Getting Started: The First 3 Hours of Pain

Install Bun and immediately hit your first problem - it conflicts with existing Node.js setups. Check the install docs but expect PATH conflicts:

## This will probably break your existing Node setup temporarily
curl -fsSL https://bun.sh/install | bash

## You'll need to restart your terminal or manually source
source ~/.bashrc

## Create project and install dependencies
mkdir pain-api && cd pain-api
bun init -y

Package Installation Hell:
Your first bun install will probably fail on some packages. The Awesome Bun compatibility list tracks what works. Here's what definitely breaks, probably more I haven't found yet:

• sharp - use @squoosh/lib instead
• bcrypt - switch to argon2
• node-canvas - good luck, just don't use it
• puppeteer - use playwright instead

Keep a Node.js environment around for testing packages before committing.

Project Structure That Actually Scales

Stop cargo-culting folder structures. The Hono starter templates are minimal but this structure works after 8 months in production:

src/
├── lib/
│   ├── db.ts              # Database connection + schema exports
│   ├── auth.ts            # JWT utilities (you'll write your own)
│   └── env.ts             # Environment validation with Zod
├── routes/
│   ├── auth.ts            # Login/logout/refresh
│   ├── users.ts           # CRUD operations
│   └── admin.ts           # Admin-only endpoints
├── middleware/
│   ├── auth.ts            # JWT verification (breaks frequently)
│   ├── cors.ts            # CORS that actually works
│   └── rate-limit.ts      # Rate limiting (required for prod)
└── index.ts               # App entry point

Database Connection That Won't Fuck You:

// src/lib/db.ts
import { drizzle } from 'drizzle-orm/postgres-js';
import postgres from 'postgres';

// This fucking config took me like 3 days to get right for Lambda. The [Drizzle connection guide](https://orm.drizzle.team/docs/get-started-postgresql) doesn't cover serverless gotchas - kept getting \"too many clients\" errors in prod because I was using the default connection pool settings. Turns out Lambda containers can spawn way faster than Postgres can handle concurrent connections:
const connectionString = process.env.DATABASE_URL!;

const sql = postgres(connectionString, {
  max: 1,                   // CRITICAL: Only 1 connection for serverless
  idle_timeout: 20,         // Prevents zombie connections
  max_lifetime: 60 * 30,    // 30 min max connection life
  prepare: false,           // Disable prepared statements (breaks in Lambda)
});

export const db = drizzle(sql);

// Schema exports (keep it simple)
export * from './schema';

Schema Definition Reality Check:

// src/lib/schema.ts
import { pgTable, serial, varchar, timestamp, boolean, text } from 'drizzle-orm/pg-core';

export const users = pgTable('users', {
  id: serial('id').primaryKey(),
  email: varchar('email', { length: 255 }).notNull().unique(),
  name: varchar('name', { length: 100 }).notNull(),
  hashedPassword: text('hashed_password').notNull(), // Use text, not varchar for hashes
  isActive: boolean('is_active').default(true),
  createdAt: timestamp('created_at').defaultNow(),
  updatedAt: timestamp('updated_at').defaultNow(),
});

// Type inference (this part actually works well)
export type User = typeof users.$inferSelect;
export type NewUser = typeof users.$inferInsert;
export type UserWithoutPassword = Omit<User, 'hashedPassword'>;

Authentication That Doesn't Suck

Forget about finding good auth middleware. The Hono JWT middleware is basic but works. You'll end up writing your own:

// src/middleware/auth.ts
import { createMiddleware } from 'hono/factory';
import { verify } from 'hono/jwt';
import type { User } from '../lib/db';

export const authMiddleware = createMiddleware<{
  Variables: {
    user: User;
  }
}>(async (c, next) => {
  const token = c.req.header('Authorization')?.replace('Bearer ', '');

  if (!token) {
    return c.json({ error: 'No token provided' }, 401);
  }

  try {
    const payload = await verify(token, process.env.JWT_SECRET!);
    const user = await getUserById(payload.sub); // You'll write this

    if (!user) {
      return c.json({ error: 'Invalid token' }, 401);
    }

    c.set('user', user);
    await next();
  } catch (error) {
    return c.json({ error: 'Invalid token' }, 401);
  }
});

Production Dockerfile That Actually Works

Don't use Alpine. Seriously. I wasted an entire weekend debugging some SSL bullshit that only happened in production - local Docker worked fine, staging worked fine, but prod was throwing random certificate validation errors on about 20% of HTTPS requests. Spent Saturday morning thinking it was our load balancer, then Saturday afternoon convinced it was our reverse proxy config. Sunday morning I was reading Alpine Linux SSL documentation trying to figure out certificate store differences. Finally just said fuck it and switched to Ubuntu base images. Boom, SSL errors gone. The Bun Docker guide recommends Ubuntu but doesn't explain why Alpine breaks:

## Use Ubuntu, not Alpine (learned this the hard way)
FROM ubuntu:22.04

## Install Bun (this will take forever the first time)
RUN apt-get update && apt-get install -y curl unzip
RUN curl -fsSL https://bun.sh/install | bash
ENV PATH=\"/root/.bun/bin:${PATH}\"

WORKDIR /app

## Copy package files
COPY package.json bun.lockb ./

## Install dependencies (some will probably fail)
RUN bun install --frozen-lockfile

## Copy source
COPY . .

## Production environment
ENV NODE_ENV=production

EXPOSE 3000

## Use bun to run the app
CMD [\"bun\", \"run\", \"src/index.ts\"]

Environment Variables You'll Actually Need

## .env (don't commit this shit)
DATABASE_URL=\"postgresql://user:password@localhost:5432/db\"
JWT_SECRET=\"your-secret-here-make-it-long\"
CORS_ORIGIN=\"http://localhost:3000\"
NODE_ENV=\"development\"

## For production, also add:
REDIS_URL=\"redis://localhost:6379\"  # For rate limiting
SENTRY_DSN=\"your-sentry-dsn\"        # For error tracking

The Deployment Script That Works

#!/bin/bash
## deploy.sh - Deploy to AWS Lambda with Bun custom runtime

## Build for Lambda
bun build src/index.ts --outdir dist --target node

## Create deployment package
cd dist && zip -r ../deploy.zip . && cd ..

## Upload to Lambda (you'll need AWS CLI configured)
aws lambda update-function-code \
  --function-name your-api \
  --zip-file fileb://deploy.zip

## Update function configuration for Bun runtime
aws lambda update-function-configuration \
  --function-name your-api \
  --runtime provided.al2 \
  --handler index.handler

This setup took me 3 weeks to get right. Budget time for debugging weird runtime issues, package compatibility problems, and deployment failures. The Bun Discord community helps with specific deployment issues. Check the Drizzle troubleshooting guide for database connection issues and the Hono deployment examples for platform-specific gotchas. But once it works, it's genuinely faster and cheaper than Node.js.

Now that you've seen the implementation nightmare, let's talk about how this actually stacks up against the traditional options in real production scenarios.