Advanced Earn Product Overview

ZTDX Earn is an on-chain fixed-income product built on smart contracts. Users subscribe USDT during the subscription window, lock funds until maturity, and then claim principal plus interest.

Key Features

• Token: USDT (6 decimal precision)
• Credential: ERC-1155 Soulbound NFT (non-transferable)
• Interest Calculation: Interest = Principal × (Annual Rate / 365) × Lock Duration in Days

Base URL

Environment	REST API
Mainnet	https://api.ztdx.io
Testnet	https://api-sepolia.ztdx.io

Product Lifecycle

Created ──▶ Subscribing ──▶ Active ──▶ Settled ──▶ Ended
               │                          │
               └──▶ Cancelled ◀───────────┘

Status	Description
created	Product created, subscription not yet open
subscribing	Subscription window open, users can subscribe
active	Subscription closed, product running, funds locked
settled	Matured and settled, users can claim principal + interest
ended	All users have completed claiming
cancelled	Emergency cancellation (principal refundable)

Status transitions are triggered automatically by a background scheduler (polling every 60 seconds):

Trigger Condition	Transition
subscribe_start_time reached	created → subscribing
subscribe_end_time reached	subscribing → active
settle_time reached	active → settled
All users have claimed	settled → ended

NFT Status

Each subscription is represented by a Soulbound NFT with the following lifecycle:

Status	Description
created	Record created, awaiting on-chain confirmation
active	NFT minted, product running
matured	Product settled, ready to claim
redeemed	NFT burned, principal + interest claimed

Amount Precision

Important

Product fields (total_quota, min_amount, etc.) use Wei format (USDT × 10⁶), while subscription request amount uses human-readable USDT.

Context	Unit	Example
Product quota/limit fields	Wei (USDT × 10⁶)	"100000000" = 100 USDT
Annual rate field (annual_rate)	Percentage string	"900.00%"
Rate bps fields	Basis points (1% = 100 bps)	90000 = 900%
Subscribe request amount	Human-readable USDT	"100" = 100 USDT
Duration field duration_seconds	Seconds	300 = 5 minutes

Conversion Examples

// Wei → USDT display
const usdtAmount = (weiAmount / 1_000_000).toFixed(2);
// "100000000" → "100.00"
// "500000000" → "500.00"

// bps → Percentage display
const annualRatePercent = (annual_rate_bps / 100).toFixed(2) + '%';
// 90000 → "900.00%"
// 5000  → "50.00%"

EIP-712 Signature

Subscription requires an EIP-712 signature from the backend, used for on-chain verification.

Domain Separator:

Field	Value
name	ZTDX Earn
version	1
chainId	Network-dependent (e.g., 421614 for Arbitrum Sepolia)
verifyingContract	Earn contract address

Subscribe Struct:

Subscribe(address user, uint256 productId, uint256 amount, uint256 deadline)

• Signature validity: 30 minutes
• Each signature can only be used once (anti-replay)

Public Endpoints

Method	Path	Description
GET	/earn/domain	Get EIP-712 domain info
GET	/earn/products	List products (with filtering)
GET	/earn/products/:id	Get product details
GET	/earn/performance	Historical performance data

User Endpoints (JWT Required)

Method	Path	Description
GET	/earn/subscriptions	My subscription records
POST	/earn/subscribe/prepare	Prepare subscription (get signature)

Smart Contract ABI

// Subscribe (requires EIP-712 signature)
function subscribe(
    uint256 productId,
    uint256 amount,     // Wei format
    uint256 deadline,
    bytes calldata signature
) external;

// Claim principal + interest (after settlement)
function claim(uint256 productId) external;

// Emergency refund (when product is cancelled)
function emergencyClaim(uint256 productId) external;

// Query user subscription
function getSubscription(uint256 productId, address user)
    external view
    returns (
        uint256 amount,
        uint256 expectedReturn,
        uint256 actualReturn,
        uint256 subscribedAt,
        bool claimed
    );

// Query product config
function getProductConfig(uint256 productId)
    external view
    returns (
        string memory name,
        uint256 annualRateBps,
        uint256 durationDays,
        uint256 totalQuota,
        uint256 minAmount,
        uint256 maxAmountPerUser
    );

// Query product timing
function getProductTiming(uint256 productId)
    external view
    returns (
        uint256 subscribeStartTime,
        uint256 subscribeEndTime,
        uint256 settleTime,
        uint256 actualSettleTime
    );

Contract Addresses (Testnet)

Network	Contract	Address
Arbitrum Sepolia	ZTDX Earn v3	0x436dcB8a2478D636a6cC678AE7A2E4c5449cB3ba
Arbitrum Sepolia	USDT	0xb8486A01a7EaAB9e34553E7B323C9C1FAE1fA7B6

Notes

• On-chain event listener polls every ~12 seconds; subscription records may have a 12–30 second delay
• Earn NFTs are ERC-1155 Soulbound — non-transferable and non-delegable
• NFTs are automatically burned upon claiming (redeemed status)