System Architecture

PBS Knowledge follows a modern three-tier architecture with a knowledge graph database at its core.

High-Level Architecture

┌─────────────────────────────────────────────────────────────┐
│                        Frontend                              │
│                   (Svelte 5 + Vite)                         │
│  ┌─────────┐ ┌─────────┐ ┌─────────┐ ┌─────────┐           │
│  │Dashboard│ │Planning │ │ Admin   │ │ Network │           │
│  │  Views  │ │  Tools  │ │ Panels  │ │  Graph  │           │
│  └─────────┘ └─────────┘ └─────────┘ └─────────┘           │
└─────────────────────────────────────────────────────────────┘
                              │
                              │ REST API
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                        Backend                               │
│                    (Fastify + Node.js)                      │
│  ┌─────────┐ ┌─────────┐ ┌─────────┐ ┌─────────┐           │
│  │  Auth   │ │Services │ │  Jobs   │ │  Sync   │           │
│  │  SAML   │ │  Layer  │ │ BullMQ  │ │ Workers │           │
│  └─────────┘ └─────────┘ └─────────┘ └─────────┘           │
└─────────────────────────────────────────────────────────────┘
                              │
              ┌───────────────┼───────────────┐
              │               │               │
              ▼               ▼               ▼
       ┌───────────┐   ┌───────────┐   ┌───────────┐
       │TerminusDB │   │   Redis   │   │  Firebase │
       │  (Graph)  │   │  (Cache)  │   │  (Auth)   │
       └───────────┘   └───────────┘   └───────────┘

Components

Frontend (Svelte 5)

The frontend is a single-page application built with:

• Svelte 5 - Reactive UI framework with runes
• Vite - Fast build tool and dev server
• Tailwind CSS - Utility-first styling
• Cytoscape.js - Network graph visualization

Key frontend patterns:

• Schema-driven forms using Felte + AJV
• Centralized API client in lib/api.ts
• Svelte stores for state management

Backend (Fastify)

The backend is a REST API server built with:

• Fastify - High-performance Node.js framework
• TypeScript - Type-safe development
• BullMQ - Job queue for background tasks

Key backend patterns:

• Service layer for business logic
• Route handlers for HTTP endpoints
• Middleware for auth and permissions

Database (TerminusDB)

TerminusDB is a knowledge graph database that provides:

• Graph Data Model - Relationships as first-class citizens
• GraphQL API - Query and mutation interface
• Schema Validation - Type-safe data operations
• Version Control - Git-like branching for data

Supporting Services

• Redis - Job queues, caching, sessions
• Firebase - Authentication, email templates
• NGINX - Reverse proxy, SSL termination

Data Flow

Read Operations

User Request → NGINX → Backend → TerminusDB GraphQL → Response

Write Operations

User Request → NGINX → Backend → Validation → TerminusDB Mutation → Response

Background Jobs

Trigger → BullMQ Queue → Worker Process → External API/Database → Completion

External Integrations

System	Purpose	Sync Direction
Dartmouth API	People, courses, enrollments	Inbound
OpenAlex	Publications, citations	Inbound
Firebase	Authentication	Bidirectional
AWS SES	Email delivery	Outbound

Deployment

The application runs in Docker containers orchestrated by Docker Compose:

services:
  frontend: # Svelte app served by NGINX
  backend: # Fastify API server
  worker: # Background job processor
  terminusdb: # Graph database
  redis: # Queue and cache

See Deployment Guide for details.