Multi-Tenant SaaS Billing & Subscription Platform

The situation

Many B2B SaaS companies start billing with a payment provider’s hosted checkout and a few scripts. That works for a handful of flat-price plans. It stops working when sales starts offering annual contracts, seat-based tiers, usage-based add-ons and custom enterprise terms. Each exception becomes a manual step, and each manual step becomes a support ticket or a revenue leak.

Our approach

1. Model pricing as data

We start with a two-week discovery where product, finance and engineering agree on a pricing model: plans, features, meters, tiers, proration and trial rules. We store that model in the database as versioned configuration. Changing a price or adding a plan becomes an admin action with an audit trail, not a deployment.

2. Treat usage as an event stream

Product services publish usage events (API calls, seats, storage, messages) to a stream with an idempotency key. The metering service deduplicates, aggregates per tenant and billing period, and keeps the raw events so every invoice line can be traced back to its source. Late or corrected events are handled explicitly instead of silently changing past invoices.

3. Isolate tenants at the data layer

Every table carries a tenant ID, and PostgreSQL row-level security policies enforce it. The API gateway resolves the tenant from the authenticated session and sets it on each database connection. A bug in one query cannot return another customer’s data. This is the answer enterprise security reviews look for.

4. Let the payment provider do payments

We keep the source of truth for plans, usage and invoices in the platform, and use Stripe for what it does best: storing payment methods, charging cards, bank debits and retrying failed payments. Webhooks are verified, processed idempotently and reconciled nightly.

5. Give finance and customers visibility

The customer portal shows current usage, upcoming charges and invoice history, which removes most “why was I charged this?” tickets. The finance console reports MRR, expansion, churn and failed payments from the same data, so the numbers match the invoices.

How we deliver it

We ship in stages behind feature flags, starting with a shadow mode that calculates invoices alongside the existing process and flags differences. Only when the two agree for a full billing cycle do we switch customers over, plan by plan. Infrastructure is defined in Terraform and runs on AWS with automated deployments; see our cloud services.

Is this relevant to you?

If your pricing is limited by what your billing code can handle, or enterprise deals stall on data-isolation questions, this architecture is a good fit. Explore our custom software development service or talk to us about your pricing model.