Fastify Framework Choice for AI Backend

Fastify Framework Choice for AI Backend

Context

The Hotpot Tracker AI backend requires a lightweight, performant Node.js framework that supports:

• High-throughput AI API requests with streaming responses
• Integration with OpenAI SDK for GPT-4 text generation
• InstantDB authentication and data access patterns
• CORS handling for frontend integration
• Minimal overhead for simple API endpoints
• TypeScript support for type safety with AI model responses

The backend serves as a bridge between the frontend application and AI services, handling:

• AI report generation with board data analysis
• User account deletion through InstantDB admin API
• Authentication validation using InstantDB refresh tokens
• Stream processing for real-time AI response delivery

Alternatives considered:

• Express.js: Industry standard but heavier with less TypeScript integration
• NestJS: Over-engineered for simple AI proxy service requirements
• Koa.js: Minimal but requires more middleware setup for TypeScript/CORS
• Hono: Newer framework with good performance but smaller ecosystem

Decision

We will use Fastify as the Node.js framework for the AI backend service.

Fastify provides:

• Excellent performance with built-in request/response validation
• First-class TypeScript support with strong type inference
• Built-in plugin system for CORS, authentication, and logging
• Efficient JSON serialization optimized for API responses
• Stream handling capabilities essential for AI response streaming
• Minimal configuration overhead for simple microservice architecture

Consequences

What becomes easier:

• High-performance API endpoints with automatic request validation
• Streaming AI responses with built-in stream handling support
• TypeScript integration provides better developer experience and type safety
• Plugin ecosystem handles CORS, logging, and authentication concerns
• Minimal boilerplate code for simple AI proxy service architecture
• Built-in request/response lifecycle hooks for monitoring and debugging

What becomes more difficult:

• Smaller community compared to Express.js ecosystem
• Learning curve for Fastify-specific patterns and plugin system
• Limited middleware options compared to Express.js ecosystem
• Potential migration complexity if requirements outgrow Fastify’s capabilities
• Less documentation and tutorials available for complex integration scenarios
• Plugin configuration may be more complex than simple Express middleware