# Cart persistence and SSR hydration

`Type:` grilling (HITL)
`Status:` open
`Blocked by:` 01

Part of [the map](../map.md).

## Question

How is a Cart identified and carried across requests? Shopify addresses a Cart by ID, and this Storefront renders on the server, so the mechanism has to survive both.

Decide: where the Cart ID lives (an httpOnly cookie the server sets, client storage, or both), what its attributes are, and how the client hydrates without a flash of an empty Cart.

Decide the failure paths too, because both are reachable: a Cart expires after 30 days, and Shopify deletes it on checkout completion — so a returning buyer can arrive holding a cookie that points at nothing. What happens then — silent re-create, cleared Cart, or an error?

## Answer

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