Coins or accounts

Chain 08

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Card payments settle into one merchant at 4,000 payments/s. Payments need p99 below 100 ms. The merchant reads its balance 20 times/s and needs a value no older than 5 seconds. Pick the ledger model.

Goals

Not tested yet

99 of 100 requests finish faster than this.The share of requests that fail or get no answer.How old the data is when a reader gets it.What the servers and services cost each month.
Choose a design
Account model: one merchant balance row
Coin model: each payment adds an unspent output
Account model with an hourly netting job