Shopping Cart & Basket Management Specification Template

Seven days is a reasonable default for most e-commerce sites. Shorter (24-48 hours) works for grocery and perishable goods where inventory changes rapidly. Longer (14-30 days) works for high-consideration purchases (furniture, electronics) where buyers research over multiple sessions. Use analytics to check when abandoned carts are recovered and set expiry just beyond the 90th percentile recovery window.

For most B2C e-commerce, show live prices that update if the catalog price changes. Notify the user when a price increases ("Price updated since you added this item") and silently apply decreases. Price-locking at add-to-cart creates liability if prices drop and customer expectations if you raise them. B2B and quote-based commerce is different: lock prices at quote acceptance.

The safest approach is additive merge: combine guest cart items with existing user cart items. If the same product exists in both, keep the higher quantity. Always show the user the merged cart with a brief notification ("We added your items to your saved cart"). Never silently replace the user's existing cart. That leads to support tickets from users who "lost" their saved items.

Set a practical maximum based on your fulfillment capacity. For general e-commerce, 50-100 items is a reasonable cap. For grocery, 150 items covers even large weekly shops. For B2B, limits may be higher. The limit exists to prevent abuse (bots loading carts to reserve inventory) and to keep the UI functional. Show a clear message when the limit is reached.

Never silently remove items. Show a clear "Out of Stock" badge on the item in the cart with options: remove, save for later (with back-in-stock notification), or view similar items. Recalculate the cart total without the out-of-stock item but keep it visible so the user understands why their total changed. Track how often this happens as an inventory health metric for your [PLG funnel](/plg-guide). ---