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Open Source SaaS API · Case study

A multi-tenant invoicing backend with isolation built in from day one

InvoicePilot is an open source SaaS API: user authentication, organisation isolation and a modular base for scalable billing systems.

The challenge

SaaS products need billing infrastructure that keeps each organisation isolated and secure from the first release, not a feature bolted on after launch.

Our approach

A multi-tenant, role-secured invoice backend with JWT authentication, organisation isolation and a modular foundation that scales as billing requirements grow.

What we built

Capabilities that do the work

Tenant isolation

Each organisation's data is separated at the data and API layers.

JWT authentication

Token-based sign-in with role checks on every endpoint.

Modular design

Billing rules live in modules, so new plans do not mean a rewrite.

Built to scale

A foundation for scalable billing systems as requirements grow.

The stack
NestJS
Structured, testable API with dependency injection.
PostgreSQL
Relational store with per-organisation scoping.
TypeORM
Typed data access and migrations.
Outcomes it was built to move
99.95% uptime
-30% billing ops time
+12% invoice collection rate

InvoicePilot is an open source capability demonstration. Outcome figures are design targets measured in demo use.

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