Documenso Reference Architecture

Overview

Production-ready architecture for Documenso document signing integrations. Covers project layout, layered service architecture, webhook processing, and data flow.

Prerequisites

• Understanding of layered architecture principles
• Documenso SDK knowledge (see documenso-sdk-patterns)
• TypeScript project with Node.js 18+

Recommended Project Structure

my-signing-app/
├── src/
│   ├── documenso/
│   │   ├── client.ts              # Singleton SDK client
│   │   ├── errors.ts              # Custom error classes
│   │   ├── retry.ts               # Retry/backoff logic
│   │   └── types.ts               # Shared types
│   ├── services/
│   │   ├── document-service.ts    # Document CRUD operations
│   │   ├── template-service.ts    # Template-based workflows
│   │   └── signing-service.ts     # Orchestrates signing flows
│   ├── webhooks/
│   │   ├── handler.ts             # Express webhook router
│   │   ├── verify.ts              # Secret verification
│   │   └── processors/
│   │       ├── document-completed.ts
│   │       ├── document-signed.ts
│   │       └── document-rejected.ts
│   ├── api/
│   │   ├── health.ts              # Health check endpoint
│   │   └── routes.ts              # API routes
│   └── config/
│       └── index.ts               # Environment configuration
├── scripts/
│   ├── verify-connection.ts       # Quick health check
│   ├── create-test-doc.ts         # Test document generator
│   └── cleanup-test-docs.ts       # Test data cleanup
├── tests/
│   ├── unit/
│   │   └── document-service.test.ts
│   ├── integration/
│   │   └── document-lifecycle.test.ts
│   └── mocks/
│       └── documenso.ts           # Mock client factory
├── .env.development
├── .env.production
├── docker-compose.yml             # Self-hosted Documenso (dev)
└── package.json

Layer Architecture

┌─────────────────────────────────────────────────────────┐
│  API / Controllers                                       │
│  Routes, request validation, response formatting         │
├─────────────────────────────────────────────────────────┤
│  Service Layer                                           │
│  Business logic, orchestration, authorization            │
│  (document-service, template-service, signing-service)   │
├─────────────────────────────────────────────────────────┤
│  Documenso Client Layer                                  │
│  SDK wrapper, retry, error handling, caching             │
│  (client.ts, retry.ts, errors.ts)                       │
├─────────────────────────────────────────────────────────┤
│  External Services                                       │
│  Documenso API, S3/GCS storage, email, database         │
└─────────────────────────────────────────────────────────┘

Rules:

• Controllers never call Documenso directly -- always go through services
• Services never import @documenso/sdk-typescript directly -- use the client wrapper
• Webhook processors are isolated -- one file per event type
• Error handling happens at the client layer, not in controllers

Data Flow

User Request
     │
     ▼
┌──────────┐   POST /api/sign
│   API    │──────────────────────────────┐
│  Router  │                              │
└──────────┘                              ▼
                                   ┌──────────────┐
                                   │   Signing    │
                                   │   Service    │
                                   └──────┬───────┘
                                          │
                    ┌─────────────────────┼─────────────────────┐
                    ▼                     ▼                     ▼
             ┌──────────┐         ┌──────────┐          ┌──────────┐
             │ Template │         │ Document │          │   Your   │
             │ Service  │         │ Service  │          │    DB    │
             └────┬─────┘         └────┬─────┘          └──────────┘
                  │                    │
                  └────────┬───────────┘
                           ▼
                    ┌──────────────┐
                    │  Documenso   │
                    │  Client      │──→ Documenso API
                    │  (singleton) │
                    └──────────────┘

Webhook Flow:
Documenso API ──POST──→ /webhooks/documenso
                             │
                        ┌────▼────┐
                        │ Verify  │──→ Check X-Documenso-Secret
                        │ Secret  │
                        └────┬────┘
                             │
                        ┌────▼────┐
                        │ Router  │──→ Route by event type
                        └────┬────┘
                             │
              ┌──────────────┼──────────────┐
              ▼              ▼              ▼
        completed.ts    signed.ts     rejected.ts
        (archive PDF)  (update DB)  (alert sender)

Setup Script

#!/bin/bash
set -euo pipefail

mkdir -p src/{documenso,services,webhooks/processors,api,config}
mkdir -p scripts tests/{unit,integration,mocks}

# Create .env.example
cat > .env.example << 'EOF'
DOCUMENSO_API_KEY=
DOCUMENSO_BASE_URL=https://app.documenso.com/api/v2
DOCUMENSO_WEBHOOK_SECRET=
LOG_LEVEL=info
NODE_ENV=development
EOF

echo "Project scaffolded. Copy .env.example to .env and fill in values."

Key Design Decisions

Decision	Rationale
Singleton client	Avoids re-initialization overhead per request
Service layer	Separates business logic from API details
One processor per webhook event	Isolates side effects, easy to test
Mock client for tests	Fast unit tests without API calls
Template-first approach	Fewer API calls, consistent field placement

Error Handling

Issue	Cause	Solution
Circular dependencies	Wrong layering	Services import client, never the reverse
Config not loading	Wrong env file	Verify NODE_ENV matches config loader
Webhook processor crash	Unhandled error in processor	Wrap each processor in try/catch
Test isolation	Shared client state	Call resetClient() in beforeEach

Resources

• Clean Architecture
• Documenso SDK
• 12-Factor App

Next Steps

For multi-environment setup, see documenso-multi-env-setup.