VietBilling Engineering Guides

Build subscription billing on PayOS from real failure modes.

Code-backed guides, diagrams, and production checklists for Vietnamese SaaS founders and developers.

01 · 10 min read

Subscription billing architecture for SaaS products on PayOS

Design Customer, Checkout, Payment, Subscription, and entitlement flows without treating a browser redirect as proof of payment.

02 · 11 min read

Build retry-safe webhook processing that never grants access twice and can recover when requests or callbacks are interrupted.

03 · 9 min read

Model renewal orders, payment links, grace periods, and access when the customer actively pays again for every billing period.

04 · 12 min read

A practical VND SaaS data model with versioned prices, historical snapshots, subscription state, and payment-independent entitlements.

05 · 14 min read

A server-to-server guide from API keys, Customers, and Checkouts to verified webhooks that activate subscriptions in your app.

06 · 8 min read

Compare code ownership, operational work, and failure modes between direct payment links and a managed billing lifecycle.