Advanced · 4–6 weeks
Multi-Tenant SaaS Billing Platform
B2B SaaS billing: tenants, subscription plans, usage metering, invoicing, and payment webhook handling. Tenant isolation at DB level, plan upgrades/downgrades, and prorated billing logic.
Why this project
Multi-tenancy and billing are senior-level staples. Demonstrates schema design, isolation strategies, and idempotent webhook processing.
Tech stack
Java 17Spring Boot 3PostgreSQLRedisStripe webhooksFlywayTestcontainers
Skills demonstrated
- Multi-tenancy
- Webhook idempotency
- Subscription lifecycle
- Usage metering
Interview talking points
- Tenant isolation trade-offs
- Idempotent Stripe webhooks
- Proration calculation
- Handling failed payments and dunning
Problem statement
B2B SaaS products need to charge customers based on plans and metered usage while keeping tenant data fully isolated and payments 100% reliable — no double-charging, no missed webhooks.