Solidity Solidity Gas Optimization

Question 1

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

Accepted Answer

calldata

Answer

Calldata is the cheapest because it is read-only and stored in the transaction input data, requiring no SSTORE or MSTORE opcodes.

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

EIP-2929 introduced cold/warm storage access: first access costs 2100 gas, subsequent accesses in the same transaction cost only 100 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

The EVM natively works with 32-byte (256-bit) values; using smaller integer types triggers extra masking/padding opcodes unless they are packed together in structs.

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

When consecutive struct members fit within 32 bytes, Solidity packs them into one slot, reducing the number of expensive storage reads/writes.

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

View and pure functions called externally via `eth_call` (not in a transaction) are executed locally by the node and cost zero gas.

Solidity Practice Test

Solidity Practice Test

Solidity Solidity Gas Optimization