The Mempool
Every transaction passes through a mempool before a block producer picks it up. How it gets prioritised depends on the chain. Toggle between fee-market and deterministic-fee mode to see the difference.
Two regimes, one queue
Bitcoin and most UTxO chains run a fee market. You bid against everyone else. Higher fees jump the queue, low-fee transactions can sit there for hours when the chain is busy. Wallets estimate the going rate so users don’t under- or overpay.
Cardano took a different route. The minimum fee is deterministic: min_fee = a·size + b, with protocol-set constants a ≈ 0.000044 ₳/byte and b ≈ 0.155381 ₳. Plutus transactions add a script-execution cost based on declared memory and CPU steps (priced by the protocol’s executionUnitPrices), so a complex contract costs more than a plain transfer. There is still no bidding and no “tip the miner”: two identical transactions always cost the same.
Why eUTxO mempools differ structurally
On account-model chains, transactions from the same account are serialized by nonce: each nonce can be used once, and replacements compete via fee bumps. On eUTxO, two transactions only conflict if they spend the same UTxO. Independent transactions don’t have to wait on each other and can be ordered freely within a block, so the mempool dynamics are fundamentally different even before you get to fee-market questions.
Three quick questions
Optional. Score 3/3 to earn mastery badges. Your first attempt counts for the Polymath badge. Questions and answer order are randomised on every attempt.
