The local-first document and email engine.

What is Relay?

Relay is a privacy-first, fully local application designed to generate dynamic LaTeX PDFs and dispatch bulk emails directly from your machine. No cloud subscriptions. No vendor lock-in. Your CSV data and SMTP credentials never leave your hard drive.

Tech Stack

Component	Technology	Purpose
Frontend	Next.js 15 (React 19), TailwindCSS	High-performance, reactive user interface
Backend API	Next.js API Routes (Node.js)	Orchestrates email queuing and PDF generation logic
Database	PostgreSQL + Prisma ORM	Stores templates, audiences, and dispatch queues securely
PDF Engine	Express + Docker (pdflatex)	Isolated microservice for lightning-fast LaTeX compilation
Mail Dispatcher	Node.js Worker (worker.js)	Background job processor for throttling SMTP connections
Auth	NextAuth.js	Secure user session management

Comprehensive Feature List

• Zero-Cost BYO-SMTP: Connect your own AWS SES, Resend, or local Exchange server.
• Dynamic LaTeX Engine: Inject CSV data straight into LaTeX templates to generate un-forgeable, pixel-perfect certificates, invoices, and contracts.
• Audience Management: Upload CSV files, auto-detect variables, and save Audience Lists with custom JSON metadata.
• Templates Studio: Design HTML, Markdown, and LaTeX templates using a built-in Monaco code editor with instant variable interpolation.
• PDF Encryption: Securely lock generated PDFs with 256-bit AES encryption using unique passwords derived from your CSV data.
• Open Tracking: Transparent 1x1 tracking pixels automatically injected to track email open rates.
• Resilient Background Worker: A decoupled background Node.js queue handles heavy SMTP sending, ensuring your dashboard never hangs during a 10,000 email blast.
• Offline Privacy: Perfect for HR and Finance. Salaries and SSNs stay strictly on your local network.

System Architecture

graph TD
    A[User / Web Browser] -->|HTTP / UI| B(Next.js App / Port 3000)
    B -->|Prisma| C[(PostgreSQL Database)]
    B -->|API Request| D[LaTeX Microservice / Port 5050]
    D -->|Exec pdflatex| E[Local File System]
    F[Background Worker] -->|Polls Queue| C
    F -->|Sends Mail| G[SMTP Provider / Resend]
    F -->|Reads PDFs| E

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Database Schema (PostgreSQL)

erDiagram
    User ||--o{ Project : "owns"
    User ||--o{ Template : "owns"
    User ||--o{ EmailQueue : "owns"
    User ||--o{ AudienceList : "owns"
    
    Template ||--o{ EmailQueue : "used as attachment"
    Project ||--o{ EmailQueue : "contains"
    
    AudienceList ||--o{ Contact : "contains"

    User {
        String id PK
        String email UK
        String smtpHost
        String resendKey
    }
    
    Template {
        String id PK
        String name
        String content
        String format "html, markdown, latex"
        String variables
    }
    
    EmailQueue {
        String id PK
        String toEmail
        String subject
        String status "pending, sent, failed"
        DateTime openedAt
    }
    
    AudienceList {
        String id PK
        String name
    }
    
    Contact {
        String id PK
        String email
        String firstName
        String metadata "JSON attributes"
    }

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Getting Started

The "One-Click" Docker Method (Recommended)

You can run the entire platform—Frontend, Background Worker, LaTeX Engine, and PostgreSQL Database—using a single command.

1. Rename .env.example to .env and fill in your keys (or leave default for local Postgres).
2. Run Docker Compose from the root:

docker-compose up -d --build

This spins up all 4 microservices instantly. The dashboard will be available at http://localhost:3000.

(Note: If you prefer to use Neon.tech or a cloud Postgres provider, just update DATABASE_URL in .env and you can optionally comment out the db service in docker-compose.yml).

The Manual Dev Method

If you want to run the stack natively without full Docker:

1. Start the LaTeX compiler: cd latex-service && docker-compose up -d
2. Run the Web App: npm install && npm run dev
3. Run the Worker: node worker.js (in a separate terminal)

4. Configuration

Create a .env.local file with your credentials:

# Database Connection
DATABASE_URL="postgresql://user:pass@host/db"

# Authentication Secret
NEXTAUTH_SECRET="your-super-secret-key"

# Email Provider
RESEND_API_KEY="re_123456789"

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Built for engineers who care about privacy, speed, and owning their data.