NFT marketplace

Key components:

User interface

• REST APIs: Express JS, typescript language
• Front-end part: Next JS, Tailwind CSS as a low-level framework
• Blockchain part: Flow network, cadence language

Video & image uploads
AWS MediaConvert to compress and convert video content:

Lambda function to crop and upload image content to Pinata IPFS:

Smart Contracts
Smart Contacts is a self-executing contract in form of an buyer-seller agreement contained within the code. This way, NFT vouchers are redeemed by the platform’s administration and exchanged for rewards.

Flow Contracts
The first Flow Contract implemented using Flow NonFungibleToken contains the following features:

• Admin-level permission creator events
• Create/update events
• Deployer-level functionality
  – Mint Non-Fungible tokens
  – Batch Mint tokens
• Metadata updates (information updates for specific NFT tokens, for example, image/video links)
• Asset storage

Along with additional getters and helpers.

The second Flow Contract implemented using Flow NonFungibleToken contains the following features:

• Several events (Withdraw, Deposit, Redeem, Consume)
  – Redeem – this function allows to take ownership over an NFT voucher from within a vault
  – Consume – this function allows to consume an NFT voucher (destroy it)
• Collection resources
• Deployer-level functionality:
  – Mint Non-Fungible tokens
  – Batch Mint tokens
• Asset storage

Along with additional getters and helpers.

Ethereum Contracts
The created contract is based on:

• ERC721A contract (ERC721A standard supports minting multiple tokens for almost the price of one)
• Ownable module (a module that provides an access control mechanism, which means owner accounts can get exclusive access to certain platform features)
• MerkleProof feature (a feature that deals with verification of datasets without re-computing the data)
• ReentrancyGuard module (a modifier that helps prevent reentrant calls to a function)

The implemented contract contains:

• Several methods of minting
  – Whitelist minting
  – Batch minting
  – Minting by an address
• Fund withdrawal
• Validation modifiers for minting
• Metadata getters and setters

Code infrastructure
For the 100% safe and smooth creation, modification and setup of infrastructure, our team picked Terraform. The solution now has two environments, for staging and production.
A diagram of the created infrastructure:

A diagram explaining the core functionality of the NFT marketplace:

During the project’s scope, our team faced challenges related to:

1.    The creation of a reliable system for configuration and minting of vouchers 

The client was using shell scripts to generate NFT tokens, but aimed to do it by using the administration panel.

We created: 

• A stepper for the system’s administrator to generate and customize NFT tokens and vouchers 
• Background services for minting and distribution

2.    The integration of several payment methods: MoonPay, MetaMask, and Flow 

One of the problems was handling several different payment methods with completely different APIs and flows. To integrate the different payment methods, we created a gateway for the different APIs and unified the whole payment process by using the Queue, WebHook and Background services.

3.    The synchronization of data from blockchain with database 

It might be difficult to trace the bought NFT tokens as they can be easily purchased on some external sources. To provide simplified monitoring, we implemented Graffle WebHooks together with Cron Jobs.