When I put food out for the street cats, there is no queue. There is a shape. The bold ones eat first, the patient ones eat second, and the one who hangs back near the hedge eats whatever is left, which on a good night is plenty and on a bad night is nothing.

Nobody is in charge of that ordering. It emerges, every evening, from how much each cat is willing to risk to get to the bowl sooner.

Bitcoin's fee market works exactly like this, and understanding it is the difference between paying what a transaction is worth and paying whatever the wallet's default button suggested.

1. The Mempool Is the Waiting Area

When you send a transaction it does not go straight into the blockchain. It goes into the mempool — a holding area, kept independently by every node, containing every valid transaction that hasn't been confirmed yet.

Roughly every ten minutes, a miner assembles the next block. Block space is limited, and the mempool is usually fuller than the next block can hold. So the miner has to choose.

They choose the way anyone would: by picking the transactions that pay them the most. Not the largest transactions — the ones offering the most fee per unit of space.

2. You Pay for Size, Not for Amount

This is the single most misunderstood thing about bitcoin fees, so it's worth being blunt.

The fee has nothing to do with how much money you're sending. Moving €5 and moving €5,000,000 cost the same, if the transactions occupy the same space.

What determines space is the structure of the transaction — how many inputs it consumes and how many outputs it creates. A transaction assembled from thirty small previous payments is physically large and expensive. A transaction spending one clean input is small and cheap, no matter what it's worth.

Fees are quoted in sats per virtual byte (sat/vB). That's your bid for space. The block fills from the highest bid downward, and everything below the cutoff waits for the next one.

3. Choosing Your Bid

The mempool is public — you can look at the current bidding on any mempool explorer, or better, on your own node. The decision is then simple:

• Not urgent? Bid low and wait. Fees follow a rhythm: quieter at weekends and during off-hours, busier when the market is moving. A transaction that isn't in a hurry can sit for hours or days and confirm when the pressure drops. This is free money and almost nobody takes it.
• Urgent? Bid at or above the current top of the mempool. You are competing for the next block, and being second is the same as being nowhere.
• Consolidating? Do it deliberately, when fees are at their quietest. Merging small inputs while nobody else is bidding is the cheapest housekeeping in bitcoin — though remember what consolidation publishes about which coins you control.

4. When You Bid Wrong

Two escape hatches exist and every self-custody user should know they're there before they need them.

• RBF (Replace-By-Fee). If your wallet flagged the transaction as replaceable, you can rebroadcast the same payment with a higher fee to jump the queue. Most modern wallets support this. Learn where the button is now, not during the wait.
• CPFP (Child Pays For Parent). If you're the recipient of a stuck transaction, you can spend its output with a high fee attached. Miners must include the parent to collect on the child, so they pull both in together. It's the cat at the back nudging the bold one forward because it's the only way to reach the bowl.

And the honest third option: nothing. A transaction that never confirms eventually drops out of mempools and the coins were never gone. Frightening the first time. Not fatal.

5. Why This Gets More Important, Not Less

As the block subsidy halves toward zero, fees have to carry more of the cost of securing the network. That means the fee market is not a temporary annoyance to be engineered away — it is the long-term business model.

Which is also the strongest practical argument for Lightning. The base layer becomes the settlement layer for things worth settling, and the daily traffic moves to the flap. Both layers doing what they're actually built for.

The Point

The colony sorts itself every night without a manager, a ticket machine, or anyone's permission — just individual cats making a judgement about how much to risk for how much sooner.

Bitcoin's fee market is the same auction, run every ten minutes, in the open, where you can watch the bidding before you place yours. The only real mistake is not looking: hitting the default fee, in the middle of a busy hour, for a payment that could have waited until Sunday morning.

Look at the mempool before you bid. The bowl is still there in an hour. 🐾⚡

Not financial advice — I feed cats and write about Bitcoin, which qualifies me for neither profession. Fee conditions change constantly; check current rates yourself before sending.