A block has room for roughly 4 million weight units and miners fill it with whatever pays best per byte. So the mempool is not a queue — it is a price ladder. Your transaction is not waiting its turn; it is waiting for everything that outbids it to clear. Set a fee rate and watch which block takes you.
Why bands, not a queue
Miners are solving a knapsack problem with one dimension that matters: satoshis per virtual byte. Total fee is irrelevant to whether you get in — a large transaction paying a lot in absolute terms still loses to a small one paying more per byte. That is why the paid amount and the fee rate are two different sliders above, and only one of them changes your position.
Grouping the pending set into bands makes the ladder legible. Each band is a price tier; the next block drains from the top down until it runs out of room. Whatever tier the block stops in becomes the cutoff — the market-clearing price for the next ten minutes. Everything below it waits for the next auction.
This is a simulation, not a live feed. Arrivals are drawn from a heavy-tailed distribution shaped to look like a real fee market, and blocks are mined on a fixed cadence rather than a Poisson process. It is built to make the mechanism visible, not to price your actual transaction.