From Prototype to Product: Adding Multi-Tenant Architecture

Day 28 of building our AI-powered FinOps platform in public

This week marked a major milestone - we finally added proper multi-tenant support. Our platform went from a single-user prototype to something that can actually serve multiple organizations.

The Single-User Problem

Our original setup was essentially:

Single user → All data mixed together

Everything was stored in one big bucket. AWS costs, resources, metrics - all mixed together with no way to separate different organizations' data. It was fine for a prototype, but completely unusable as a real product.

Building Multi-Tenancy from Scratch

We restructured everything to support proper multi-tenant architecture:

Tenant → AWS Projects → Resources/Costs/Metrics

This wasn't just adding a tenant field - it was building the entire concept of organizational separation:

Database Architecture

• Added tenant isolation across all tables

• Created AWS project structure within each tenant

• Built proper data separation and access controls

API Layer

• Every endpoint now validates tenant access

• Added comprehensive data isolation

• Built project-aware operations for each tenant

Why This Structure

Organizations don't just have one AWS account. They typically manage:

• Separate dev, staging, and production environments

• Multiple accounts across business units

• Resources distributed across regions

Our new structure lets each tenant (organization) manage multiple AWS projects, matching how they actually organize their infrastructure.

The Challenge

This was essentially rebuilding the entire platform. Every database table, every API endpoint, every frontend component had to be made tenant-aware.

What made it manageable was our TDD + AI approach:

1. Write tests defining how tenant isolation should work

2. Use AI to help implement the complex multi-tenant logic

3. Iterate until all data is properly isolated

The Result

Before: "Show me AWS costs" → Mixed data from everywhere After: "Show me costs for Organization ABC's production environment" → Clean, isolated insights

We went from a single-user demo to a platform that can serve multiple organizations simultaneously.

Key Insights

1. Multi-tenancy changes everything - It's not just adding a field, it's rethinking your entire data model

2. Build it early - Adding multi-tenancy later is much harder than designing for it upfront

3. Comprehensive testing is crucial - Data leakage between tenants would be catastrophic

This was one of those weeks where progress felt slow but was actually huge. We now have the foundation to serve real customers instead of just running demos.

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Have you built multi-tenant systems? The complexity always surprises me - would love to hear about your experiences.