Tutorials on building paid SaaS products with FastAPI: billing, EU VAT, accounts and deployment. Real code, and the parts that went wrong the first time.
Argon2 passwords, signed-cookie sessions you can revoke, email links without a tokens table, a single-use reset link and Bearer tokens for the API.
Stripe Tax in Checkout, why VAT numbers should be checked before they reach Stripe, and what to do when VIES is down.
Checkout, a local copy of subscriptions in PostgreSQL, webhooks that survive duplicates and reordering, and the race between the success page and the webhook.