🔥 Gas Fees Demystified: The Ultimate Guide to Efficient Smart Contracts

⛽ Understanding Ethereum Gas Fundamentals

Gas Components

• ⛽ Gas Units: Computational work measured in wei
• 💰 Gas Price: Gwei per unit (1 Gwei = 0.000000001 ETH)
• 📈 Gas Limit: Maximum units user will pay for

Cost Calculation

Total Cost = Gas Used * (Base Fee + Priority Fee)

Example: 100,000 gas * (15 Gwei + 2 Gwei) = 1.7 ETH

🚀 Top 15 Gas Optimization Strategies

1. Memory vs Storage Management

❌ Inefficient

function updateUser() public {
    user.storageVar1 = 1; // 20,000 gas
    user.storageVar2 = 2; // 20,000 gas
}

✅ Optimized

function updateUser() public {
    User memory temp = user;
    temp.var1 = 1; // Memory write: 3 gas
    temp.var2 = 2; // Memory write: 3 gas
    user = temp; // Single storage write: 20,000 gas
}

💡 Savings: 20,000 gas per additional storage write

2. Data Packing & Struct Optimization

❌ Wasted Storage

struct User {
    uint256 id;     // Slot 0
    uint8 status;   // Slot 1 (wastes 31 bytes)
    uint256 balance;// Slot 2
}

✅ Packed Storage

struct User {
    uint256 id;     // Slot 0
    uint8 status;   // Slot 1
    uint248 balance;// Slot 1 (fills remaining space)
}

Data Type	Size	Gas Cost
Storage Write	32 bytes	20,000 gas
Memory Write	Any size	3 gas

3. Loop Optimization Techniques

❌ Dangerous Pattern

for(uint i = 0; i < array.length; i++) {
    // O(n) gas cost risk
    process(array[i]);
}

⚠️ Gas cost increases linearly with array size

✅ Optimized Approach

uint256 length = array.length; // Cache array length
for(uint i = 0; i < length;) {
    process(array[i]);
    unchecked { i++; } // Save gas on overflow checks
}

💡 40% gas reduction on large loops

🛠️ Advanced Optimization Strategies

🔄 Batch Processing

function bulkTransfer(
    address[] calldata recipients,
    uint256[] calldata amounts
) external {
    // Calldata cheaper than memory
}

📦 Assembly Optimization

function rawBalance(address addr) view public returns(uint) {
    assembly {
        let result := balance(addr)
        mstore(0x0, result)
        return(0x0, 32)
    }
}

🔧 Gas Optimization Toolbox

Tool	Purpose	Gas Savings
Hardhat Gas Reporter	Test gas costs	Up to 30%
EVM Dialect	Assembly optimization	15-50%
SSTORE2/SLOAD2	Storage patterns	Up to 40%

🚨 Critical Mistakes to Avoid

💸 Expensive Operations

• Unbounded loops
• Excessive storage writes
• String concatenation

🔓 Security Risks

• Ignoring overflow checks
• Unchecked call returns
• Reentrancy vulnerabilities

📈 Real-World Optimization Case Study

ERC-20 Contract Gas Reduction:

Optimization	Before	After	Savings
Storage Layout	150k gas	92k gas	38%
Batch Transfers	85k gas/tx	23k gas/tx	73%

✅ Gas Optimization Checklist

• 🔲 Use calldata instead of memory
• 🔲 Pack structs efficiently
• 🔲 Use unchecked math where safe
• 🔲 Cache storage variables
• 🔲 Minimize storage writes
• 🔲 Use bitwise operations
• 🔲 Avoid expensive opcodes
• 🔲 Use custom errors