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Marcus Sterling

Marcus Sterling

Verified Contributor

Full-Stack System Architect

London, UK
Web Applications & SaaS

SaaS Multi-Tenant Billing Core

Enterprise Next.js dashboard with Stripe subscriptions and dynamic RBAC security

12,000+Users in Week 1
$1.4M+ARR Processed
48msP95 Page Load
99.9%Payment Success

Project Overview

Built a high-performance, multi-tenant SaaS application core featuring dark/light theming, granular permission roles (Admin, Editor, Member), and real-time subscription lifecycle management.

The Challenge

The client needed to launch their enterprise SaaS product in under 4 weeks with complex tier-based usage limits and seamless Stripe checkout integration.

The Architecture Solution

Delivered a modular Next.js 14 platform with Tailwind CSS, FastAPI asynchronous REST microservices, and Stripe Webhook event listeners managing customer subscription states.

Technical Architecture Highlights

  • Next.js 14 App Router with React Server Components for sub-50ms initial page loads.
  • Custom Stripe billing engine with invoice PDF generation, proration logic, and customer portal.
  • JWT and HTTP-only cookie authentication with role-based middleware guards.
  • Optimistic UI updates with SWR/React Query for instantaneous dashboard responsiveness.

Key Features & Capabilities

Multi-Tenant Isolation

Complete data segregation between organizations with custom tenant subdomains.

Stripe Subscription Engine

Supports recurring monthly/annual plans, usage metering, one-off upgrades, and trial periods.

Audit Log & Activity Feed

Tracks every team action, login attempt, and permission modification with timestamped audit logs.

Exportable Analytics

Interactive charts with one-click export to CSV, Excel, and branded executive PDF reports.

RareBros delivered our SaaS platform ahead of schedule. The code was exceptionally clean, well-tested, and handled our 12,000 user launch without breaking a sweat.

Elena RostovaFounder, MetricPulse SaaS

Technology Stack

Next.js 14Tailwind CSSFastAPIStripe Billing APIPostgreSQLRedisTypeScript

About the Contributor

Full-stack specialist with deep expertise in Next.js App Router, Stripe custom billing engines, and enterprise RBAC authorization systems.

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