OpenZeppelin ERC721Enumerable vs Azuki ERC721A

In this repo, we are going to be using Hardhat to measure relative gas costs for:

• OpenZeppelin ERC721Enumerable, vs.
• Azuki ERC721A

And then deploying a sample ERC721A contract using Alchemy

If you want to run this code yourself:

1. git clone [email protected]:thatguyintech/demo-erc721a.git
2. npm install
3. npx hardhat test

Let's dig in. First..

• Validate the blog post
  • mint 1 piece up to 5 pieces (batch)
  • compare gas costs

thatguyintech@albert demo-erc721a % npx hardhat test


OpenZeppelin ERC721Enumerable
	gas to mint 1 104138
	gas to mint 2 219626
	gas to mint 3 335114
	gas to mint 4 450602
	gas to mint 5 566090

Azuki ERC721A
	gas to mint 1 93704
	gas to mint 2 96212
	gas to mint 3 98720
	gas to mint 4 101228
	gas to mint 5 103736

You can see from the above results that the findings in the original Azuki ERC721A blog post are true. Batch-minting 5 pieces using the ERC721A implementation costs around the same (or less!) compared to batch minting only 1 piece using the ERC721Enumerable implementation.

Pretty cool stuff.

However, I also wanted to know if there are any downsides to using ERC721A, and indeed there are some negative tradeoffs:

After a user batch mints some NFTs, depending on which tokenId they subsequently transfer, the gas costs may increase linearly.

thatguyintech@albert demo-erc721a % npx hardhat test


OpenZeppelin ERC721Enumerable
	minted 1, transfered id: 0, cost: 69655
	minted 2, transfered id: 1, cost: 90367
	minted 2, transfered id: 0, cost: 95210
	minted 3, transfered id: 2, cost: 90367
	minted 3, transfered id: 1, cost: 100822
	minted 3, transfered id: 0, cost: 95210
	minted 4, transfered id: 3, cost: 90367
	minted 4, transfered id: 2, cost: 100822
	minted 4, transfered id: 1, cost: 100822
	minted 4, transfered id: 0, cost: 95210
	minted 5, transfered id: 4, cost: 90367
	minted 5, transfered id: 3, cost: 100822
	minted 5, transfered id: 2, cost: 100822
	minted 5, transfered id: 1, cost: 100822
	minted 5, transfered id: 0, cost: 95210

Azuki ERC721A
	minted 1, transfered id: 0, cost: 71355
	minted 2, transfered id: 1, cost: 91197
	minted 2, transfered id: 0, cost: 92043
	minted 3, transfered id: 2, cost: 93927
	minted 3, transfered id: 1, cost: 111885
	minted 3, transfered id: 0, cost: 92043
	minted 4, transfered id: 3, cost: 96657
	minted 4, transfered id: 2, cost: 114615
	minted 4, transfered id: 1, cost: 111885
	minted 4, transfered id: 0, cost: 92043
	minted 5, transfered id: 4, cost: 99387
	minted 5, transfered id: 3, cost: 117345
	minted 5, transfered id: 2, cost: 114615
	minted 5, transfered id: 1, cost: 111885
	minted 5, transfered id: 0, cost: 92043

translated to an table for legibility:

(read x-axis then y-axis, for example: "Mint 1 then transfer tokenId 0" or "Mint 4 then transfer tokenId 3")

OpenZeppelin ERC721Enumerable:

	Mint 1	Mint 2	Mint 3	Mint 4	Mint 5
t0	69655	95210	95210	95210	95210
t1		90367	100822	100822	100822
t2			90367	100822	100822
t3				90367	100822
t4					90367

Azuki ERC721A:

	Mint 1	Mint 2	Mint 3	Mint 4	Mint 5
t0	71355	92043	92043	92043	92043
t1		91197	111885	111885	117345
t2			93927	114615	114615
t3				96657	111885
t4					99387

We can see that the cost to mint higher-numbered tokenIDs increases when the original batch mint size increases.

Although it sucks to see this linear cost increase for transfers solely based on which tokenID you want to transfer, there is a workaround:

https://twitter.com/fulldecent/status/1491506122565595141?s=20&t=rystKohzG5MkxONXxxvFxA

1. Always mint the maximum allowed
2. Transfer out your ODD numbered tokens first in ascending order
3. Then transfer out your EVEN numbered tokens

Also, for most people, the impact of ERC721A on transfer might not matter too much. The mint function is much more important because it is the first impression that people have of the project.

If the fees are high, they will be sad. If the fees are low, they will be happy.

Transfers are rare and only happen every once in a while.

TODO..

• Create a new contract that inherits from the ERC721A contract

  • Deploy to Rinkeby! Use the Rinkeby Faucet.

• Build a frontend site that displays the gas costs when a user mints