Cloudflare D1 Skill

Cloudflare D1 is a serverless SQLite database designed for Cloudflare Workers with global distribution and zero cold starts.

Sources: D1 Docs | Drizzle + D1 | Wrangler CLI

Core Principle

SQLite at the edge, migrations in version control, Drizzle for type safety.

D1 brings SQLite's simplicity to serverless. Design for horizontal scale (multiple small databases) rather than vertical (one large database). Use Drizzle ORM for type-safe queries and migrations.

D1 Stack

Project Setup

Create Worker Project

# Create new project
npm create cloudflare@latest my-app -- --template "worker-typescript"
cd my-app

# Install dependencies
npm install drizzle-orm
npm install -D drizzle-kit

Create D1 Database

# Create database (creates both local and remote)
npx wrangler d1 create my-database

# Output:
# [[d1_databases]]
# binding = "DB"
# database_name = "my-database"
# database_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"

Configure wrangler.toml

name = "my-app"
main = "src/index.ts"
compatibility_date = "2024-01-01"

[[d1_databases]]
binding = "DB"
database_name = "my-database"
database_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
migrations_dir = "drizzle"
migrations_table = "drizzle_migrations"

Generate TypeScript Types

# Generate env types from wrangler.toml
npx wrangler types

# Creates worker-configuration.d.ts:
# interface Env {
#   DB: D1Database;
# }

Drizzle ORM Setup

Schema Definition

// src/db/schema.ts
import { sqliteTable, text, integer, real, blob } from 'drizzle-orm/sqlite-core';
import { sql } from 'drizzle-orm';

export const users = sqliteTable('users', {
  id: integer('id').primaryKey({ autoIncrement: true }),
  email: text('email').notNull().unique(),
  name: text('name').notNull(),
  role: text('role', { enum: ['user', 'admin'] }).default('user'),
  createdAt: text('created_at').default(sql`CURRENT_TIMESTAMP`),
  updatedAt: text('updated_at').default(sql`CURRENT_TIMESTAMP`)
});

export const posts = sqliteTable('posts', {
  id: integer('id').primaryKey({ autoIncrement: true }),
  title: text('title').notNull(),
  content: text('content'),
  authorId: integer('author_id').references(() => users.id),
  published: integer('published', { mode: 'boolean' }).default(false),
  viewCount: integer('view_count').default(0),
  createdAt: text('created_at').default(sql`CURRENT_TIMESTAMP`)
});

export const tags = sqliteTable('tags', {
  id: integer('id').primaryKey({ autoIncrement: true }),
  name: text('name').notNull().unique()
});

export const postTags = sqliteTable('post_tags', {
  postId: integer('post_id').references(() => posts.id),
  tagId: integer('tag_id').references(() => tags.id)
});

// Type exports
export type User = typeof users.$inferSelect;
export type NewUser = typeof users.$inferInsert;
export type Post = typeof posts.$inferSelect;
export type NewPost = typeof posts.$inferInsert;

Drizzle Config

// drizzle.config.ts
import { defineConfig } from 'drizzle-kit';

export default defineConfig({
  schema: './src/db/schema.ts',
  out: './drizzle',
  dialect: 'sqlite',
  driver: 'd1-http',
  dbCredentials: {
    accountId: process.env.CLOUDFLARE_ACCOUNT_ID!,
    databaseId: process.env.CLOUDFLARE_DATABASE_ID!,
    token: process.env.CLOUDFLARE_D1_TOKEN!
  }
});

Database Client

// src/db/index.ts
import { drizzle } from 'drizzle-orm/d1';
import * as schema from './schema';

export function createDb(d1: D1Database) {
  return drizzle(d1, { schema });
}

export type Database = ReturnType<typeof createDb>;
export * from './schema';

Migration Workflow

Generate Migration

# Generate migration from schema changes
npx drizzle-kit generate

# Output: drizzle/0000_initial.sql

Apply Migrations Locally

# Apply to local D1
npx wrangler d1 migrations apply my-database --local

# Or via Drizzle
npx drizzle-kit migrate

Apply Migrations to Production

# Apply to remote D1
npx wrangler d1 migrations apply my-database --remote

# Preview first (dry run)
npx wrangler d1 migrations apply my-database --remote --dry-run

Migration File Example

-- drizzle/0000_initial.sql
CREATE TABLE `users` (
  `id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
  `email` text NOT NULL,
  `name` text NOT NULL,
  `role` text DEFAULT 'user',
  `created_at` text DEFAULT CURRENT_TIMESTAMP,
  `updated_at` text DEFAULT CURRENT_TIMESTAMP
);

CREATE UNIQUE INDEX `users_email_unique` ON `users` (`email`);

CREATE TABLE `posts` (
  `id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
  `title` text NOT NULL,
  `content` text,
  `author_id` integer REFERENCES `users`(`id`),
  `published` integer DEFAULT false,
  `view_count` integer DEFAULT 0,
  `created_at` text DEFAULT CURRENT_TIMESTAMP
);

Worker Implementation

Basic Worker with Hono

// src/index.ts
import { Hono } from 'hono';
import { createDb, users, posts } from './db';
import { eq, desc } from 'drizzle-orm';

type Bindings = {
  DB: D1Database;
};

const app = new Hono<{ Bindings: Bindings }>();

// Middleware to inject db
app.use('*', async (c, next) => {
  c.set('db', createDb(c.env.DB));
  await next();
});

// List users
app.get('/users', async (c) => {
  const db = c.get('db');
  const allUsers = await db.select().from(users);
  return c.json(allUsers);
});

// Get user by ID
app.get('/users/:id', async (c) => {
  const db = c.get('db');
  const id = parseInt(c.req.param('id'));

  const user = await db.select().from(users).where(eq(users.id, id)).get();

  if (!user) {
    return c.json({ error: 'User not found' }, 404);
  }
  return c.json(user);
});

// Create user
app.post('/users', async (c) => {
  const db = c.get('db');
  const body = await c.req.json<{ email: string; name: string }>();

  const result = await db.insert(users).values({
    email: body.email,
    name: body.name
  }).returning();

  return c.json(result[0], 201);
});

// Update user
app.put('/users/:id', async (c) => {
  const db = c.get('db');
  const id = parseInt(c.req.param('id'));
  const body = await c.req.json<Partial<{ email: string; name: string }>>();

  const result = await db.update(users)
    .set({ ...body, updatedAt: new Date().toISOString() })
    .where(eq(users.id, id))
    .returning();

  if (result.length === 0) {
    return c.json({ error: 'User not found' }, 404);
  }
  return c.json(result[0]);
});

// Delete user
app.delete('/users/:id', async (c) => {
  const db = c.get('db');
  const id = parseInt(c.req.param('id'));

  const result = await db.delete(users).where(eq(users.id, id)).returning();

  if (result.length === 0) {
    return c.json({ error: 'User not found' }, 404);
  }
  return c.json({ deleted: true });
});

export default app;

Raw D1 API (Without ORM)

// src/index.ts
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);

    if (url.pathname === '/users' && request.method === 'GET') {
      const { results } = await env.DB.prepare(
        'SELECT * FROM users ORDER BY created_at DESC'
      ).all();
      return Response.json(results);
    }

    if (url.pathname === '/users' && request.method === 'POST') {
      const body = await request.json() as { email: string; name: string };

      const result = await env.DB.prepare(
        'INSERT INTO users (email, name) VALUES (?, ?) RETURNING *'
      ).bind(body.email, body.name).first();

      return Response.json(result, { status: 201 });
    }

    return new Response('Not Found', { status: 404 });
  }
};

Query Patterns

Select Queries

import { eq, and, or, like, gt, desc, asc, count, sql } from 'drizzle-orm';

// Basic select
const allPosts = await db.select().from(posts);

// Select specific columns
const titles = await db.select({ id: posts.id, title: posts.title }).from(posts);

// Where clause
const published = await db.select().from(posts).where(eq(posts.published, true));

// Multiple conditions
const recentPublished = await db.select().from(posts).where(
  and(
    eq(posts.published, true),
    gt(posts.createdAt, '2024-01-01')
  )
);

// OR conditions
const featured = await db.select().from(posts).where(
  or(
    eq(posts.viewCount, 1000),
    like(posts.title, '%featured%')
  )
);

// Order and limit
const topPosts = await db.select()
  .from(posts)
  .orderBy(desc(posts.viewCount))
  .limit(10);

// Pagination
const page2 = await db.select()
  .from(posts)
  .orderBy(desc(posts.createdAt))
  .limit(10)
  .offset(10);

// Count
const postCount = await db.select({ count: count() }).from(posts);

Joins

// Inner join
const postsWithAuthors = await db.select({
  post: posts,
  author: users
})
.from(posts)
.innerJoin(users, eq(posts.authorId, users.id));

// Left join
const allPostsWithAuthors = await db.select()
  .from(posts)
  .leftJoin(users, eq(posts.authorId, users.id));

// Many-to-many via junction table
const postsWithTags = await db.select({
  post: posts,
  tag: tags
})
.from(posts)
.leftJoin(postTags, eq(posts.id, postTags.postId))
.leftJoin(tags, eq(postTags.tagId, tags.id));

Insert, Update, Delete

// Insert single
const newUser = await db.insert(users).values({
  email: 'user@example.com',
  name: 'John Doe'
}).returning();

// Insert multiple
await db.insert(users).values([
  { email: 'a@test.com', name: 'Alice' },
  { email: 'b@test.com', name: 'Bob' }
]);

// Upsert (insert or update on conflict)
await db.insert(users)
  .values({ email: 'user@test.com', name: 'New Name' })
  .onConflictDoUpdate({
    target: users.email,
    set: { name: 'New Name' }
  });

// Update
await db.update(posts)
  .set({ published: true })
  .where(eq(posts.id, 1));

// Update with increment
await db.update(posts)
  .set({ viewCount: sql`${posts.viewCount} + 1` })
  .where(eq(posts.id, 1));

// Delete
await db.delete(posts).where(eq(posts.id, 1));

Transactions

// D1 supports transactions via batch
const results = await db.batch([
  db.insert(users).values({ email: 'a@test.com', name: 'A' }),
  db.insert(users).values({ email: 'b@test.com', name: 'B' }),
  db.update(posts).set({ published: true }).where(eq(posts.id, 1))
]);

// Raw D1 batch
const batchResults = await env.DB.batch([
  env.DB.prepare('INSERT INTO users (email, name) VALUES (?, ?)').bind('a@test.com', 'A'),
  env.DB.prepare('INSERT INTO users (email, name) VALUES (?, ?)').bind('b@test.com', 'B')
]);

Local Development

Start Dev Server

# Local development with D1
npx wrangler dev

# With specific port
npx wrangler dev --port 8787

Database Management

# Execute SQL locally
npx wrangler d1 execute my-database --local --command "SELECT * FROM users"

# Execute SQL file
npx wrangler d1 execute my-database --local --file ./seed.sql

# Open SQLite shell
npx wrangler d1 execute my-database --local --command ".tables"

Drizzle Studio

# Run Drizzle Studio for visual DB management
npx drizzle-kit studio

Seed Data

-- seed.sql
INSERT INTO users (email, name, role) VALUES
  ('admin@example.com', 'Admin User', 'admin'),
  ('user@example.com', 'Test User', 'user');

INSERT INTO posts (title, content, author_id, published) VALUES
  ('First Post', 'Hello World!', 1, true),
  ('Draft Post', 'Work in progress...', 1, false);

# Seed local database
npx wrangler d1 execute my-database --local --file ./seed.sql

Multi-Environment Setup

wrangler.toml

name = "my-app"
main = "src/index.ts"
compatibility_date = "2024-01-01"

# Development
[env.dev]
[[env.dev.d1_databases]]
binding = "DB"
database_name = "my-database-dev"
database_id = "dev-database-id"

# Staging
[env.staging]
[[env.staging.d1_databases]]
binding = "DB"
database_name = "my-database-staging"
database_id = "staging-database-id"

# Production
[env.production]
[[env.production.d1_databases]]
binding = "DB"
database_name = "my-database-prod"
database_id = "prod-database-id"

Deploy to Environments

# Deploy to staging
npx wrangler deploy --env staging

# Deploy to production
npx wrangler deploy --env production

# Apply migrations to staging
npx wrangler d1 migrations apply my-database-staging --remote --env staging

Testing

Integration Tests

// tests/api.test.ts
import { unstable_dev } from 'wrangler';
import type { UnstableDevWorker } from 'wrangler';
import { describe, beforeAll, afterAll, it, expect } from 'vitest';

describe('API', () => {
  let worker: UnstableDevWorker;

  beforeAll(async () => {
    worker = await unstable_dev('src/index.ts', {
      experimental: { disableExperimentalWarning: true }
    });
  });

  afterAll(async () => {
    await worker.stop();
  });

  it('should list users', async () => {
    const res = await worker.fetch('/users');
    expect(res.status).toBe(200);
    const data = await res.json();
    expect(Array.isArray(data)).toBe(true);
  });

  it('should create user', async () => {
    const res = await worker.fetch('/users', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ email: 'test@test.com', name: 'Test' })
    });
    expect(res.status).toBe(201);
  });
});

CLI Quick Reference

# Database
wrangler d1 create <name>                    # Create database
wrangler d1 list                             # List databases
wrangler d1 info <name>                      # Database info
wrangler d1 delete <name>                    # Delete database

# Migrations
wrangler d1 migrations list <name>           # List migrations
wrangler d1 migrations apply <name> --local  # Apply locally
wrangler d1 migrations apply <name> --remote # Apply to production

# SQL execution
wrangler d1 execute <name> --command "SQL"   # Run SQL
wrangler d1 execute <name> --file ./file.sql # Run SQL file
wrangler d1 execute <name> --local           # Run on local
wrangler d1 execute <name> --remote          # Run on production

# Development
wrangler dev                                 # Start local server
wrangler types                               # Generate TypeScript types
wrangler deploy                              # Deploy to production

# Drizzle
drizzle-kit generate                         # Generate migrations
drizzle-kit migrate                          # Apply migrations
drizzle-kit studio                           # Open Drizzle Studio
drizzle-kit push                             # Push schema (dev only)

D1 Limits & Considerations

Anti-Patterns

• Single large database - Design for multiple smaller databases (per-tenant)
• No migrations - Always version control schema changes
• Raw SQL everywhere - Use Drizzle for type safety
• No connection to remote - Always test against real D1 before deploy
• Large blobs in D1 - Use R2 for file storage
• Complex joins - D1 is SQLite; keep queries simple
• No batching - Use batch for multiple operations
• Ignoring limits - Monitor usage on free tier