SaaS Growth Engine

Northstar — Full-stack B2B SaaS platform for growth operations, team collaboration, and subscription billing

Overview

SaaS Growth Engine (Northstar) is a full-stack B2B SaaS platform for managing growth operations, team collaboration, and subscription billing. Built as a production-ready monorepo with authentication, multi-tenancy, Stripe billing, analytics, and audit logging.

Architecture


┌─────────────────┐     ┌─────────────────┐     ┌─────────────────┐
│   Frontend      │────▶│    Backend      │────▶│    MongoDB      │
│   (Angular)     │     │   (NestJS)      │     │   (Atlas)       │
└─────────────────┘     └─────────────────┘     └─────────────────┘
                               │
                               ▼
                        ┌─────────────────┐
                        │    Stripe       │
                        │  (Billing)      │
                        └─────────────────┘
                               │
                               ▼
                        ┌─────────────────┐
                        │    Resend       │
                        │   (Email)       │
                        └─────────────────┘

Key Design Decisions

Monorepo for shared types, simplified CI, atomic commits
MongoDB for flexible tenant-scoped documents; indexes created automatically in dev
Hash-based routing on frontend for static hosting compatibility
Server-side authority — all billing, auth, and RBAC enforced on backend

Features Implemented

Authentication & Identity

Email/password signup with organization creation
Email verification via one-time tokens
Password reset flow
JWT access tokens (15 min) + rotated opaque refresh cookies (7 days)
Invitation acceptance (existing or new users)

Multi-Tenancy & RBAC

Organizations with unique slugs
Roles: Admin, Manager, Viewer
Membership resolution on every protected request
Minimum-one-admin protection on role changes/removals
Organization-scoped data access

Team Management

Invite members with role selection
Role changes (Admin only)
Member removal (Admin only, self-protection)
Pending invitations with revocation
Paginated member listing

Billing & Subscriptions (Stripe)

3 Plans: Starter, Growth, Scale — prices fetched live from Stripe
Server-created Checkout Sessions (subscription mode)
Customer Portal for self-service management
Webhook handling with signature verification
Idempotent event processing (duplicate-safe)
Subscription state sync: created/updated/deleted, invoice paid/failed
Plan availability gated by configured Stripe Price IDs

Analytics Dashboard

MRR (Monthly Recurring Revenue) with currency support
Churn rate calculation
Active subscription count
New member growth (30-day rolling)
Monthly growth bar chart
Date-range filtering (max 366 days)

Audit Logging

Immutable event log per organization
Redacted metadata (passwords, tokens, emails masked)
Admin-only access
Paginated, newest-first

Workspace Settings

Organization name update (Admin only)
Workspace ID display
Sign out

UI/UX

Responsive layout (desktop sidebar → mobile bottom nav)
Light/Dark theme (CSS variables, persisted)
Loading, empty, and error states
Accessible markup (ARIA, semantic HTML)

Project Structure

                
saas-growth-engine/
├── backend/
│   ├── src/
│   │   ├── main.ts                 # App bootstrap, raw body for webhooks
│   │   ├── app.module.ts           # Module imports, global config
│   │   ├── config/environment.ts   # Zod-validated env schema
│   │   ├── modules/
│   │   │   ├── database/           # Mongoose models, connection, retry
│   │   │   ├── auth/               # Signup, login, tokens, guards
│   │   │   ├── users/              # Member CRUD, invitations
│   │   │   ├── organizations/      # Org settings, current org
│   │   │   ├── billing/            # Stripe integration, webhooks
│   │   │   ├── analytics/          # Aggregation pipelines
│   │   │   ├── audit/              # Audit log recording
│   │   │   └── email/              # Resend service
│   │   └── ...
│   └── package.json
├── frontend/
│   ├── src/app/
│   │   ├── app.ts                  # Main component, state, API calls
│   │   ├── app.html                # Template (all sections)
│   │   ├── app.scss                # Styles (CSS variables, responsive)
│   │   ├── core/
│   │   │   ├── api.service.ts      # HTTP client, token refresh
│   │   │   └── auth.interceptor.ts # Auto-attach auth, 401 retry
│   │   └── app.routes.ts           # Hash routes for billing pages
│   └── package.json
├── vercel.json                     # Frontend deploy config
├── render.yaml                     # Backend deploy config
├── .env.example                    # Environment template
└── pnpm-workspace.yaml

Challenges & Solutions

Hash routing + static hosting

Avoids server config complexity for SPAs by using hash-based routing.

Idempotent webhooks

Critical for Stripe; use unique event IDs + status locking to prevent duplicate processing.

Retry with backoff

MongoDB Atlas cold starts need connection retries with exponential backoff.

Server-side price fetching

Keeps frontend in sync with Stripe Dashboard by fetching prices at runtime.

Environment validation at startup

Fails fast with clear messages using Zod-validated environment schema.

Future Enhancements

Team workspaces (multiple orgs per user)
Usage-based billing / metered prices
Email templates with React Email
Webhook retry dashboard
API keys for programmatic access
Slack/Discord notifications
Export analytics to CSV

Deployment

Frontend

Vercel

Backend

Render

Database

MongoDB Atlas

CI/CD

GitHub Actions

Tech Stack

NestJSAngularMongoDBStripeTypeScriptpnpm