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You can set the SELL Minimum Mining Fee Per Byte and Maximum Mining Fee Per Byte settings. When you set these numbers, you ensure that your transactions are processed within a defined fee range. The “X rolling” fee calculation is still used, but it will never be less (or more) than the range you set here.
Minimum Mining Fee Per Byte
Minimum Mining Fee Per Byte ensures that the transaction is never submitted to the network with a trivial fee. The vast majority of “stuck” transactions involve fees of 1 sat/byte (or even less).
Set too high: your profitability suffers.
Set to zero (default) or too low, and the “stuck” transaction will eventually happen.
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The bottom layer is “0-1” sat/byte. In the past week, most every transaction fell into this fee range, and many cleared during the week. Transactions over 10 sat/byte cleared within an hour (or less).
Between Sep 18 - Sep 24, the only transactions that cleared had fees over 17 sat/byte.
In this case, a minimum fee of 10 sat/byte may have been vulnerable to being “stuck”.
This vulnerability was only a problem if the CAS algorithm erroneously calculated a fee based on the last X transactions' fees not exceeding 17 sat/byte. In other words, the conditions would have had to be “perfect” for the CAS algorithm to fail to post a proper fee. This rarely happens, but it isn’t impossible.
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In this chart, a minimum fee of 140 sat/byte would have been vulnerable at some point.
And 6+ years:
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In this chart, a minimum fee of 300 400 sat/byte would have been vulnerable at some point.
The takeaway is: there is no “perfect” minimum. You will always be vulnerable as long as you are profitable. Paying 300x 400x the average mining fees to assure you avoid any delay is unreasonable (and expensive).
The best advice? Set it to 2 sat/byte (or slightly higher). This will mitigate the problem for most transactions, while still retaining some level of profitability.
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