Process one-time virtual item purchases in a Roblox experience using Developer Products

Steps

1. Create the Developer Product for the experience (via Studio or Open Cloud's Developer Products configuration endpoints, which manage the product definition, not the purchase itself)
2. Call MarketplaceService:PromptProductPurchase(player, productId) in Luau to show the native purchase UI to the player
3. Implement MarketplaceService.ProcessReceipt as a callback that grants the item and must return Enum.ProductPurchaseDecision.PurchaseGranted (or NotProcessedYet if you can't process it yet)
4. Make ProcessReceipt idempotent and non-blocking, since Roblox will retry delivering the same receipt until your callback returns a definitive decision
5. Do not use PromptProductPurchaseFinished to grant items — it fires when the purchase prompt closes, not when payment is actually confirmed
6. Log granted receipts server-side so you can audit against Roblox's transaction records if a player disputes a purchase