> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cronozen.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Architecture Overview

> Cronozen platform architecture — hub-and-spoke multi-tenant SaaS OS

# Architecture Overview

## The Problem

Korea's social service industry — child rehabilitation, welfare, education, pharmacy — still runs on **fragmented legacy systems**.

| Reality                               | Consequence                             |
| ------------------------------------- | --------------------------------------- |
| Each center adopts separate solutions | Data silos, duplicate investment        |
| Manual records + spreadsheets         | No audit trail, compliance risk         |
| AI adoption attempts                  | No decision provenance, trust failure   |
| Voucher/policy changes                | Manual updates, errors, revenue leakage |

The core problem isn't just "digital transformation." It's the absence of an architecture that can answer: **"Who verified an AI decision, how, and why?"**

## The Solution

Cronozen is a full-stack platform with **Decision Proof Unit (DPU)** as its core primitive. Three design principles:

1. **Provable Decisions** — Every AI recommendation is sealed in a DPU envelope with evidence, confidence scores, risk levels, and approval chains
2. **One Backend, Infinite Context** — Rehab centers, welfare agencies, pharmacies all run on the same infrastructure with fully isolated tenant contexts
3. **Policy as Runtime** — National, regional, and center-level policies are automatically applied at runtime with temporal validity

## Hub-and-Spoke Ecosystem

```
┌─────────────────────────────────────────────────────────────┐
│                      CLIENT LAYER                            │
│                                                              │
│   slowpace.co.kr    cronozen.com    learn.cronozen.com      │
│        │                │                │                   │
│        └────────────────┼────────────────┘                   │
│                         │  Domain Router                     │
│                         ▼                                    │
├──────────────────────────────────────────────────────────────┤
│                   EDGE MIDDLEWARE                             │
│          JWT Auth · RBAC · Tenant Resolution · Rate Limit    │
├──────────────────────────────────────────────────────────────┤
│                                                              │
│                   APPLICATION LAYER                           │
│                   (Next.js 16 + TypeScript)                   │
│                                                              │
│  ┌──────────┐  ┌──────────────┐  ┌──────────┐  ┌─────────┐ │
│  │ API      │  │ AI System    │  │ Policy   │  │ Agent   │ │
│  │ Routes   │  │              │  │ Engine   │  │ Orchest.│ │
│  │          │  │ Multi-       │  │          │  │         │ │
│  │ REST +   │  │ Provider     │  │ 4-Scope  │  │ Workflow│ │
│  │ Server   │  │ RAG + NL→SQL │  │ Resolve  │  │ Engine  │ │
│  │ Actions  │  │ 6W Extract.  │  │ Temporal │  │         │ │
│  └────┬─────┘  └──────┬───────┘  └────┬─────┘  └───┬─────┘ │
│       │               │               │             │       │
│       └───────────────┼───────────────┼─────────────┘       │
│                       ▼               ▼                      │
│  ┌───────────────────────────────────────────────────────┐  │
│  │            DPU ENGINE (Decision Proof Unit)             │  │
│  │                                                         │  │
│  │  ┌─────────────┐  ┌─────────────┐  ┌────────────────┐ │  │
│  │  │ dpu-core    │  │ dpu-pro     │  │ dpu-connector  │ │  │
│  │  │ Hash Chain  │  │ 5 Govern.   │  │ -prisma        │ │  │
│  │  │ Canonical.  │  │ Guards      │  │ DB Adapter     │ │  │
│  │  │ Envelope    │  │ Compliance  │  │                │ │  │
│  │  └─────────────┘  └─────────────┘  └────────────────┘ │  │
│  └───────────────────────────────────────────────────────┘  │
│                              │                               │
├──────────────────────────────┼───────────────────────────────┤
│                        DATA LAYER                            │
│                                                              │
│  ┌──────────────────┐  ┌──────────────┐  ┌──────────────┐  │
│  │ PostgreSQL       │  │ pgvector     │  │ Redis        │  │
│  │ 200+ Tables      │  │ Embeddings   │  │ Cache +      │  │
│  │ Prisma 6.18      │  │ Similarity   │  │ Session      │  │
│  └──────────────────┘  └──────────────┘  └──────────────┘  │
│                                                              │
│           Security: Tenant Isolation · Audit Logging         │
└──────────────────────────────────────────────────────────────┘
```

### OPS Hub

The central hub manages all cross-cutting concerns:

* **SSO** — Single sign-on via `auth.cronozen.com`
* **Payments** — Toss Payments, subscription management, billing
* **Tenant Master** — Center/workspace provisioning and lifecycle
* **DPU** — Decision Proof Unit with SHA-256 hash chains
* **7 Verticals** — Rehabilitation, welfare, education, pharmacy, commerce, mentoring, interior

### Spoke Services

| Service  | Domain             | Focus                                     |
| -------- | ------------------ | ----------------------------------------- |
| **LMS**  | learn.cronozen.com | Learning engine, HRD-Net compliance, EMON |
| **CMS**  | blog.cronozen.com  | Blog, manuals, content management         |
| **ERP**  | erp.cronozen.com   | Business management (Odoo-based)          |
| **Docs** | docs.cronozen.com  | Developer documentation (Mintlify)        |

## 7 Verticals

All verticals share the same codebase, differentiated by tenant configuration:

| Code      | Vertical             | Description                                 |
| --------- | -------------------- | ------------------------------------------- |
| Rehab     | Child Rehabilitation | Voucher-based therapy session management    |
| Welfare   | Welfare Benefits     | Benefit application, processing, settlement |
| Edu       | Education Centers    | Enrollment, curriculum, attendance          |
| Pharmacy  | Pharmacy             | Prescription tracking, inventory            |
| Market    | Commerce             | Coupons, promotions, local economy          |
| Mentoring | Mentoring            | Expert matching, session tracking           |
| Interior  | Interior             | Space design, construction management       |

Each vertical uses **Centers** as the isolation boundary. Centers have workspaces, and within workspaces all data, permissions, and policies are scoped.

## Tech Stack

| Layer    | Technology                              |
| -------- | --------------------------------------- |
| Frontend | Next.js 16, TypeScript, Tailwind CSS    |
| Backend  | Next.js API Routes (134+), Prisma 6.18  |
| Database | PostgreSQL (pgvector), Redis            |
| Auth     | JWT, SSO, multi-tenant session          |
| AI       | Multi-provider (OpenAI, Claude, Gemini) |
| Infra    | AWS ECS Fargate, ECR, S3, CloudFront    |
| DNS/CDN  | CloudFlare                              |
| CI/CD    | GitHub Actions                          |

## Data Flow

```
Client Request
  → CloudFlare (DNS + WAF + Worker for white-label)
    → ECS Fargate (Next.js 16)
      → Edge Middleware (JWT + tenant resolution)
        → API Route (scoped to center_id)
          → Prisma 6.18 (row-level tenant isolation)
            → PostgreSQL (RDS, VPC internal)
```

## Deployment Strategy

| Branch    | Environment | URL              | Auto-deploy |
| --------- | ----------- | ---------------- | ----------- |
| `develop` | Staging     | stg.cronozen.com | Yes         |
| `main`    | Production  | cronozen.com     | Yes         |

All repos follow the same pattern: `develop` → staging, `main` → production.

## Security Architecture

* **Tenant Isolation**: Row-level via `center_id` scoping in Prisma middleware
* **Auth**: JWT with multi-tenant context, actor family linking
* **Audit**: Append-only logs, 12 event types, `basePrisma` usage audited
* **Cron**: All 39 cron routes require `verifyCronSecret()`
* **Data Access**: All center access through `center_memberships` only — no backdoor

<Info>
  For deep dives into specific subsystems, see [Multi-Tenant Architecture](/architecture/multi-tenant), [DPU Engine](/architecture/dpu), and [Proof Pipeline](/architecture/proof-pipeline).
</Info>