Solidity Solidity Gas Optimization 2

Question 1

What is the gas cost benefit of using `immutable` vs regular state variables in Solidity?

Accepted Answer

Immutable values are embedded in bytecode and read with cheap PUSH opcodes instead of SLOAD

Answer

Immutable variables are baked into the contract bytecode at deployment, so reading them costs only a few gas (PUSH opcode) instead of the 100–2100 gas of SLOAD.

Question 2

What is the `constant` keyword in Solidity and how does it save gas compared to storage variables?

Accepted Answer

Constants are inlined at compile time as literal values, using zero gas to read

Answer

Constants are replaced by their literal values during compilation, so accessing them requires no storage read at all — they are embedded directly in the bytecode.

Question 3

How does short-circuiting in Solidity boolean expressions help with gas optimization?

Accepted Answer

If the first condition of `&&` is false, the second is not evaluated, saving the gas for the expensive check

Answer

In `A && B`, if A is false, B is skipped; placing cheap conditions first avoids executing expensive ones unnecessarily.

Question 4

What gas saving does using `bytes32` instead of `string` for fixed-length identifiers provide?

Accepted Answer

bytes32 is stored in a single slot with no length prefix, while string uses dynamic encoding with extra overhead

Answer

A `bytes32` occupies exactly one 32-byte storage slot with no extra length or pointer overhead, while short strings under 32 bytes still use dynamic encoding in some contexts.

Question 5

Why does emitting events instead of storing data in storage save gas in Solidity?

Accepted Answer

Events are stored in transaction logs, which cost ~8 gas/byte vs 20,000 gas for new storage writes

Answer

Writing to storage (SSTORE) costs 20,000 gas for a new slot, while event logs cost approximately 375 gas plus ~8 gas per byte of data.

Solidity Practice Test

Solidity Practice Test

Solidity Solidity Gas Optimization 2