Cart or balance

Quorum 10

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A shop keeps carts and balances in two clusters of 3 copies. At 0:20 a fault cuts each primary off from its followers for 10 s. A shopper must always be able to add an item. A debit may be refused during the cut, but it must never be lost.

Goals

Not tested yet

Saved data that was lost later.The share of requests that fail or get no answer.The share of requests that get a correct answer.What the servers and services cost each month.
Choose a design
Accept writes everywhere, last write wins
Accept writes only with a majority
Carts accept and merge, balances need a majority