best way to handle instructions that need to be executed on the user side and on the back end side?

Question

I have a process to purchase compressed nft but go through our contract first.

in the process I'm making now. I made an api on the backend, when the user presses the buy button, the backend will mint compressed nft using the wallet authority, then delegate to our contract program.

Only then did I give the mint results to the user side to be able to buy through our program contract delegation bridge earlier.

what I want to ask, is there a more efficient way than the method I above? Is there a way that my 2 instructions can be combined into one instruction? with my signer user and wallet authority?

because with the method above, I have to make 2 instructions in the program namely "mint_by_authority" and the function "buy_nft"

because when the mint compressed nft process I use verified creators, which means there must be signer creators.

Therefore, my method above separates the mint process from being done on the backend side, then the mint results are delegated to the program so that users can buy them.

if anyone gives suggestions the most effective way I'm open, thanks

Answer 1

what I did here https://github.com/solana-developers/one-milion-nfts/blob/main/next/pages/api/mint.ts is send a request to the backend, partial sign it, base64 encode it, send it back to client, deserialize and and then sign in the frontend as well. Like this you can get both signers and you could also add a payment for the NFT.