Solidity Solidity Gas Optimization

Question 1

Which storage location is the cheapest in terms of gas cost in Solidity?

Accepted Answer

calldata

Answer

memory

Answer

storage

Answer

transient storage

Question 2

What is the gas cost difference between SLOAD (reading storage) in a cold vs warm slot in EIP-2929?

Accepted Answer

Cold: 2100 gas, Warm: 100 gas

Answer

Cold: 800 gas, Warm: 200 gas

Answer

Cold: 5000 gas, Warm: 800 gas

Answer

Cold: 2100 gas, Warm: 800 gas

Question 3

Why is it more gas-efficient to use `uint256` instead of `uint8` or `uint128` for standalone state variables?

Accepted Answer

The EVM operates on 32-byte words, so smaller types require masking operations that cost extra gas

Answer

uint256 uses fewer storage slots than smaller types

Answer

Smaller types are deprecated in Solidity 0.8

Answer

The compiler converts all uints to uint256 at compile time anyway

Question 4

What gas optimization does Solidity variable packing in structs provide?

Accepted Answer

Multiple small variables can share a single 32-byte storage slot, reducing SSTORE/SLOAD calls

Answer

Packed structs are stored in memory instead of storage automatically

Answer

Packing removes the need for ABI encoding

Answer

It allows using calldata for struct parameters

Question 5

What is the gas benefit of marking a function as `view` or `pure`?

Accepted Answer

External callers pay zero gas when calling them off-chain via eth_call

Answer

They skip input validation entirely

Answer

They use calldata instead of memory for all parameters

Answer

They can bypass the require() checks

Question 6

Why is using `++i` preferred over `i++` in Solidity loops for gas optimization?

Accepted Answer

Post-increment creates a temporary copy of the value, costing extra gas

Answer

Pre-increment skips the overflow check in Solidity 0.8

Answer

++i uses fewer opcodes in all compiler versions

Answer

i++ is undefined behavior in Solidity