JUSD

# Savings & Interest

Earn interest on your JuiceDollars through the built-in savings module.

The JuiceDollar system includes a native savings feature that allows JUSD holders to earn interest simply by depositing their tokens. The interest rate is governed by JUICE holders through the Leadrate mechanism.

# How Savings Work

When you deposit JUSD into the savings module, your tokens start earning interest immediately. The interest accrues continuously based on the current Leadrate (base interest rate) set by governance.

# Key Features

Feature Description
No lockup period Withdraw anytime without penalty
Continuous interest Interest accrues every second
Compound on refresh Claim interest to start earning interest on interest
Governance-controlled rate JUICE holders vote on the interest rate

# The Leadrate System

The Leadrate (from German "Leitzins" - base rate) is the system-wide interest rate that affects both savings yields and borrowing costs.

# How Rates Are Set

  1. A qualified JUICE holder (with ≥2% voting power) proposes a new rate
  2. The proposal enters a 7-day timelock
  3. After 7 days, anyone can execute the change
  4. The new rate takes effect immediately
Current Rate → Proposal → 7 Day Wait → New Rate Active

# Rate Mechanics

The Leadrate uses a "ticks" system for precise interest calculation:

  • 1 tick = 1 PPM-second (parts per million per second)
  • Interest accumulates as ticks over time
  • When you refresh your balance, ticks are converted to JUSD

Example: At 5% annual rate (50,000 PPM):

  • 1 day = 50,000 × 86,400 = 4,320,000,000 ticks
  • On 10,000 JUSD = ~1.37 JUSD interest per day

# Using the Savings Module

# Depositing JUSD

To start earning interest:

  1. Navigate to the Savings page on the JuiceDollar app (opens new window)
  2. Enter the amount of JUSD you want to deposit
  3. Approve the transaction
  4. Your JUSD immediately starts earning interest

Contract function: save(uint192 amount)

# Checking Your Balance

Your savings balance consists of:

  • Principal: The JUSD you deposited
  • Accrued Interest: Interest earned since last refresh

To see your current balance including interest:

Contract function: accruedInterest(address owner) returns your pending interest

# Withdrawing JUSD

You can withdraw your JUSD plus earned interest at any time:

  1. Go to the Savings page
  2. Enter the amount to withdraw (or click "Max")
  3. Confirm the transaction
  4. Receive your JUSD plus interest

Contract function: withdraw(address target, uint192 amount)

# Refreshing Your Balance

To compound your interest (earn interest on interest):

  1. Call the refresh function periodically
  2. Your accrued interest is added to your principal
  3. Future interest is calculated on the new, higher balance

Contract function: refreshBalance(address owner)

Tip: Refresh your balance periodically to maximize compound interest gains.

# Interest Source

The interest paid to savers comes from the equity pool. This means:

  • Interest is only paid when there is sufficient equity
  • The equity() function determines available funds
  • If equity is depleted, interest payments are capped

This creates a natural balance: high savings rates attract deposits but reduce equity, while low rates preserve equity but may cause withdrawals.

# SavingsVaultJUSD (ERC-4626)

For DeFi integration, JuiceDollar provides an ERC-4626 compatible vault that wraps the savings module.

# What is ERC-4626?

ERC-4626 is the "Tokenized Vault Standard" - a standard interface for yield-bearing tokens. It allows:

  • Easy integration with DeFi protocols
  • Standardized deposit/withdraw functions
  • Automatic share price calculation

# Vault Mechanics

Concept Description
Shares (svJUSD) Represent your proportional ownership of the vault
Assets (JUSD) The underlying tokens in the vault
Price per Share Increases over time as interest accrues

Example:

  1. You deposit 1,000 JUSD when price = 1.00 → receive 1,000 svJUSD
  2. Interest accrues, price increases to 1.05
  3. Your 1,000 svJUSD is now worth 1,050 JUSD

# Vault Functions

// Deposit JUSD, receive shares
function deposit(uint256 assets, address receiver) returns (uint256 shares)

// Withdraw JUSD by specifying asset amount
function withdraw(uint256 assets, address receiver, address owner) returns (uint256 shares)

// Redeem shares for JUSD
function redeem(uint256 shares, address receiver, address owner) returns (uint256 assets)

// Check current share price
function price() returns (uint256)

// Check total assets including accrued interest
function totalAssets() returns (uint256)

# Inflation Attack Protection

The vault uses OpenZeppelin's virtual shares pattern to prevent "inflation attacks" where a malicious first depositor could manipulate share prices. A small virtual offset is added to calculations for safety.

# Contract Addresses

# Mainnet (Chain ID: 4114)

Contract Address Purpose
SavingsGateway 0x22FE239892eBC8805DA8f05eD3bc6aF75332b60b (opens new window) Main savings with frontend rewards
SavingsVaultJUSD 0x1b70ae756b1089cc5948e4f8a2AD498DF30E897d (opens new window) ERC-4626 vault adapter

# Testnet (Chain ID: 5115)

Contract Address Purpose
SavingsGateway 0x54430781b33581CE2b0DBD837CA66113BeEEFD8e (opens new window) Main savings with frontend rewards
SavingsVaultJUSD 0x802a29bD29f02c8C477Af5362f9ba88FAe39Cc7B (opens new window) ERC-4626 vault adapter

# Interest Calculation Example

Scenario:

  • Deposit: 10,000 JUSD
  • Leadrate: 4% annual (40,000 PPM)
  • Duration: 30 days

Calculation:

Daily interest = 10,000 × (40,000 / 1,000,000) / 365 = 1.096 JUSD
30-day interest = 1.096 × 30 = 32.88 JUSD

With compounding (daily refresh):

After 30 days ≈ 32.96 JUSD (slightly more due to compound effect)

# Savings vs. JUICE Investment

Aspect Savings (JUSD) Pool Shares (JUICE)
Risk Low - principal preserved Higher - value fluctuates
Return Fixed Leadrate Variable (fees + liquidations)
Governance None Voting power
Lockup None None (same-block protection only)
Best for Stable yield seekers Active participants

# Important Notes

  1. Module Disabled: The savings module is disabled when the Leadrate is 0% or about to become 0% within 3 days. Deposits are blocked in this state.

  2. Interest Cap: Interest payments are capped by available equity. In extreme scenarios, you may receive less than expected.

  3. No Insurance: Unlike traditional bank deposits, there is no deposit insurance. The safety of your funds depends on the overall health of the JuiceDollar system.

  4. Gas Costs: Consider gas costs when deciding how often to compound. For small balances, frequent refreshing may not be economical.

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