AWS Blocks Application Development

Package naming: All packages are published under the @aws-blocks scope (e.g., @aws-blocks/core, @aws-blocks/blocks, @aws-blocks/bb-kv-store).

Overview

AWS Blocks is an Infrastructure-from-Code framework where Building Blocks bundle CDK, SDK, and local mocks into a single API. It provides 18+ Building Blocks covering storage, authentication, real-time communication, background jobs, file management, AI/search, email, and observability — all working locally without AWS credentials.

Key characteristics:

• One aws-blocks/ directory defines the entire backend
• Frontend imports are fully typed — no client generation needed
• All Building Blocks work locally without AWS (mocks persist to .bb-data/)
• Deploy ephemeral, individual testing environments with npm run sandbox and long-lived environments with npm run deploy using least-privilege credentials

Scaffolding a New Project

npx @aws-blocks/create-blocks-app my-app
cd my-app

To add AWS Blocks to an existing project:

npx @aws-blocks/create-blocks-app .

This detects the existing project and adds an aws-blocks/ workspace alongside your code.

To add AWS Blocks to an Amplify Gen 2 project:

npx @aws-blocks/create-blocks-app .

When the CLI detects amplify/backend.ts, it automatically integrates AWS Blocks with your Amplify backend.

With a specific template:

npx @aws-blocks/create-blocks-app my-app --template demo
cd my-app

Available Templates

Template	Description
default	Vite + lit-html starter app with basic authentication, data persistence, and realtime to help demonstrate basic app architecture and patterns (used when --template is omitted)
bare	Vite + lit-html starter with a single "hello world" API method and a bare frontend
react	React + Vite starter with a single API endpoint and typed React frontend
backend	Backend-only — no frontend, just the AWS Blocks API with a single endpoint
demo	Todo app with AuthBasic, KVStore, DistributedTable, Zod schemas, indexes, and auth-protected CRUD
auth-cognito	Full AuthCognito passwordless email-OTP with roles, device management, and Authenticator UI
nextjs	Next.js + React starter with AWS Blocks backend integration (SSR + Server Components)

Development Workflow

After scaffolding, refer to node_modules/@aws-blocks/blocks/README.md for the complete development workflow including:

• Core concepts (Architecture, Building Block selection)
• Project structure and Scope organization
• Error handling patterns
• Schema validation
• Local development
• Best practices and common mistakes
• Deployment IAM role setup and security guidance

When implementing a specific Building Block, read its package README for the detailed API reference (e.g., node_modules/@aws-blocks/bb-kv-store/README.md). These are the authoritative docs for your installed version.

Security Considerations

• Use await auth.requireAuth(context) in every method that shouldn't be public — ApiNamespace methods are unauthenticated by default
• Use new AppSetting(scope, id, { secret: true }) for API keys and credentials — never hardcode or use .env files
• Always attach a schema to KVStore/AppSetting that accepts user data — the RPC layer validates structure but not business logic
• Do not add broad * IAM policies — each Building Block already grants least-privilege scoped to its own resources
• Never change blockPublicAccess on FileBucket — serve public files through CloudFront instead
• Configure CORS_ALLOWED_ORIGINS explicitly for production — avoid wildcards
• For cross-domain deployments, pass crossDomain: true to auth constructors (enables SameSite=None; Secure; Partitioned)
• Enable monitoring: { enabled: true, snsTopicArn: '...' } on Hosting for production alerts
• Add WAF and API Gateway throttling via CDK for public-facing apps — not included by default
• Logger provides serialization safety (circular refs, type coercion) but does NOT redact sensitive content — never pass raw credentials, tokens, or secrets to Logger methods; sanitize context objects before logging