Building a B2B SaaS platform for transport companies, I faced a critical architectural decision: separate database per tenant or shared database with logical isolation?

I chose shared database. Here's why and how I implemented bulletproof data isolation with pure Laravel.

Why Shared Database

For a B2B SaaS, database evolution is critical:

Pros:

Atomic migrations (add a column once, not 500 times)

Simplified backup/restore

Lower infrastructure costs

Cons:

Logical isolation (not physical)

Noisy neighbor risk

If I ever reach 500 tenants, managing 500 separate migrations per feature would be a full-time job. Shared DB wins.

The Architecture

USER REQUEST │ ▼ MIDDLEWARE (EnsureTenantAccess) │ 1. Verify authentication │ 2. Extract tenant ID │ 3. Store in TenantContext (singleton) ▼ ELOQUENT MODELS (with BelongsToTenant trait) │ 4.…