Regular wallets can send at most 4 transactions at once, and they need to sign the current
seq_no. This in effect limits them to 4 transactions every 5 second, and this operation need to be serialized, meaning that there needs to be a single service sending these 4 transactions.
Highload wallets can send up to 254 transactions in a single request, and they don't need a
seq_no. This way, they can send many transactions, multiple times without needing to wait between each batch, and there is no need for a single service, the operation can happen in parallel.
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