How to specify max fee in @solana/web3.js Transaction

Question

The Solana documentation says

Transactions currently include a fee field that indicates the maximum fee field a slot leader is permitted to charge to process a transaction.

(source: https://docs.solana.com/implemented-proposals/transaction-fees)

But in @solana/web3.js, the transaction builder SystemProgram.transfer only takes a from, to and amount. There is a fee calculator interface and a getEstimatedFee method in the transfer object, but I can't find how to set the maximum.

Answer 1

You don't need to specify a fee because as of now there is no eth-like fee market in Solana where people bid to get their tx included. In future, this is subject to change. To send a transfer transaction:

const transferTransaction = new Transaction().add(
  SystemProgram.transfer({
    fromPubkey: fromKeypair.publicKey,
    toPubkey: toKeypair.publicKey,
    lamports: lamportsToSend,
  })
);

await sendAndConfirmTransaction(connection, transferTransaction, [fromKeypair]);

https://solanacookbook.com/references/basic-transactions.html#how-to-send-sol