Architecture Overview

Concepts

ELVA Notify follows a layered monolith pattern: a single Node.js process exposes HTTP endpoints and delegates to service modules. Business-specific template data lives in isolated modules under src/businesses/, registered at startup via a Business Registry. Delivery paths (OTP, legacy SMS, DLT SMS, email) converge in the Notification Service.

Key design principles:

• Multi-tenant isolation — appId scopes OTP storage and authentication.
• Separation of validation and delivery — Template validation runs before DLT payload build and send.
• Provider abstraction at service level — SMS goes through sms.service.js; Fast2SMS is the current provider implementation.
• Centralized logging — Controllers do not log; services emit structured JSON via businessLogger.

Current Architecture — Component Diagram

Core Components

Business Registry

Location: src/businesses/registry.js, src/businesses/index.js

Central index of registered business modules. Provides getBusiness(), getTemplate(), listBusinesses(), listTemplates(). Businesses self-register at startup; adding a new business does not require modifying existing modules.

Business Modules

Location: src/businesses/<name>/

Each module bundles:

• config.js — businessId, display name, DLT defaults (PEID, sender ID)
• templates.js — Template catalog with variable schemas and per-template DLT IDs
• index.js — Facade exposing getTemplate(), listTemplateKeys()

Currently registered: eNandi (enandi).

Validation Layer

Location: src/services/templateValidation/

Validates /notify DLT requests:

1. Resolve business → business module
2. Resolve templateKey → template definition
3. Validate variables against schema (type, length, pattern, format)

Throws TemplateValidationError with machine-readable code on failure.

DLT Layer

Location: src/services/dltPayloadResolver.service.js

Transforms validated template + variables into Fast2SMS DLT payload:

• senderId, templateId, entityId, variablesValues (pipe-separated)

Resolution order: template DLT → business DLT → environment fallback.

Notification Layer

Location: src/services/notification.service.js

Single dispatch entry point sendNotification(). Routes by channel:

Logging Layer

Location: src/services/logging/

Categories: SYSTEM, BUSINESS, OTP, NOTIFICATION, DLT, ERROR.

All logs include: requestId, business, templateKey, channel, recipient, status, provider, templateId, businessVersion (default v1).

Folder Structure

elva-notify-platform/
├── docs/                          # Markdown documentation source
│   ├── README.md
│   ├── architecture/
│   ├── api/
│   └── businesses/
├── frontend/                      # Next.js documentation portal
├── backend/
│   ├── public/                    # API landing page (index.html)
│   ├── src/
│   │   ├── app.js                 # Express app, middleware, error handler
│   │   ├── server.js              # Startup: Redis connect, listen
│   │   ├── businesses/
│   │   │   ├── index.js           # Registry bootstrap
│   │   │   ├── registry.js        # Business Registry
│   │   │   └── enandi/
│   │   │       ├── config.js      # PEID, sender ID
│   │   │       ├── templates.js   # Template catalog
│   │   │       └── index.js       # Module facade
│   │   ├── config/
│   │   │   ├── allowedApps.js       # APP_CREDENTIALS_JSON loader
│   │   │   ├── channels.js        # SUPPORTED_CHANNELS
│   │   │   └── env.js             # Environment config
│   │   ├── controllers/
│   │   ├── middleware/
│   │   ├── routes/
│   │   ├── services/
│   │   └── utils/
│   ├── package.json
│   └── .env.example
└── package.json                   # Root orchestrator scripts

Request Processing Overview

API Surface Summary

Route mounting: health.routes.js mounts /health and /otp/*; notify.routes.js mounts /notify.

Real Request Example

POST /notify HTTP/1.1
Host: notify.elvatech.in
Content-Type: application/json

{
  "appId": "enandi-app",
  "apiKey": "your-secret-key",
  "channel": "SMS",
  "to": ["919876543210"],
  "business": "enandi",
  "templateKey": "ORDER_PLACED",
  "variables": {
    "orderId": "ORD-2026-001",
    "orderDate": "2026-06-05"
  }
}

Real Response Example

{
  "success": true,
  "message": "Notification sent",
  "channel": "SMS",
  "templateKey": "ORDER_PLACED",
  "requestId": "f47ac10b-58cc-4372-a567-0e02b2c3d479"
}

Troubleshooting Notes

Future Extensibility

• New business: Add src/businesses/<name>/, call registerBusiness() in src/businesses/index.js.
• New SMS provider: Implement provider module, wire through sms.service.js.
• OTP DLT migration: Wire OTP send path to use eNandi LOGIN_OTP template instead of route q.
• New channels: Extend SUPPORTED_CHANNELS and add handler in notification.service.js.