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Understanding how Mina transaction fees work on the `mainnet` network
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understanding-mina-transaction-fees.md

User Commands (Transactions)

What are User Commands?

User commands, commonly called transactions, are user-initiated actions on the Mina blockchain. There are two types of transactions: payment transactions and stake delegations.

  • Payment Transactions: Users send MINA to other users.
  • Stake Delegations: Users delegate their staking weight to validators (block producers) to participate in consensus and earn rewards.

Failed Transactions

User transactions can and do fail, and these scenarios must be managed accordingly. If a payment transaction fails, the sender will not be charged the transaction amount but will still be required to pay the fee to the SNARK worker. Similarly, if a stake delegation fails, the fee will be charged, but there is no payment to return.

Account Creation Fee

Transactions directed to accounts that have not previously received transactions will incur an account creation fee of 1 MINA. This applies to both user transactions and coinbase transactions.

Internal Commands

What are Internal Commands?

Internal commands are actions executed by the protocol itself rather than being initiated by users. These actions include awarding coinbase rewards and initiating fee transfers to compensate for SNARK work.

Fee Transfer

Fee transfers are used to pay prover fees to SNARK workers. A corresponding proof must be included for every transaction occupying a slot. Fee transfers can originate from transaction fees or the coinbase, with the latter being referred to as fee_transfer_via_coinbase.

If the transaction fees exceed the total SNARK work fees, the remainder will be sent to the block producer via a fee transfer. Likewise, if the transaction fees don't cover the SNARK work, the deficit will be paid from the coinbase reward.

Coinbase Transaction

These are protocol-initiated rewards given to validators for producing a block. Similar to a user transaction, there may be a fee associated with the transaction to cover SNARK work. In cases where there is no SNARK fee, the full coinbase reward will be awarded to the block producer. If the SNARK worker does charge a fee, this fee will be deducted from the coinbase reward, and the deduction will be sent to the SNARK worker through a fee_transfer_via_coinbase transfer.

There is a peculiar implementation detail where, at most, 2 coinbase transactions may be sent, which also implies that potentially, at most, 2 fee_transfer_via_coinbase transfers may occur. The coinbase reward, minus any fees, is divided equally across these two coinbase transactions.

Fee Transfer via Coinbase

Fee transfer via coinbase operates much like fee transfer, except the fee comes from the coinbase.

Preconditions for a Fee Transfer via Coinbase

  • When there are no transactions, meaning no transaction fees are available to pay for the SNARK work needed to include the coinbase transaction.

  • This includes scenarios where transactions cannot be included due to high SNARK work fees.

  • When the SNARK work fees exceed the transaction fees.

Reading Material

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