Solidity Gas Optimization in Interviews: Why Juniors Fail the Question and What Seniors Actually Look For

Victor P · 2025-10-30T06:05:58+00:00

I realized recently that I’ve been approaching “gas optimization” totally wrong in interviews. Every time the question comes up, I start dumping the usual lines — avoid storage writes, use calldata, short-circuit conditions, pack variables. It feels safe because everyone repeats these same things.But last week, a senior engineer stopped me mid-answer and said:“Okay, but how do you decide when to optimize?”And I didn’t know what to say. I froze. It suddenly hit me that I’ve been memorizing patterns instead of understanding how seniors think about gas in an actual production repo.My personal projects aren’t large enough to give me a real sense of “hot paths,” and I haven’t worked on a contract where a single SSTORE could cost thousands in aggregate. So I’m confused about what interviewers actually want — do they expect juniors to talk about profiling? Trade-offs? CEI consistency? Auditability? Or just awareness of common pitfalls?How do you answer gas-optimization questions in a way that sounds like real engineering judgment instead of parroting a checklist?

Solidity Gas Optimization in Interviews: Why Juniors Fail the Question and What Seniors Actually Look For

Victor P
@TrG6JIR

Updated: Nov 23, 2025

Views: 135

I realized recently that I’ve been approaching “gas optimization” totally wrong in interviews. Every time the question comes up, I start dumping the usual lines — avoid storage writes, use calldata, short-circuit conditions, pack variables. It feels safe because everyone repeats these same things.
But last week, a senior engineer stopped me mid-answer and said:
“Okay, but how do you decide when to optimize?”
And I didn’t know what to say. I froze. It suddenly hit me that I’ve been memorizing patterns instead of understanding how seniors think about gas in an actual production repo.
My personal projects aren’t large enough to give me a real sense of “hot paths,” and I haven’t worked on a contract where a single SSTORE could cost thousands in aggregate. So I’m confused about what interviewers actually want — do they expect juniors to talk about profiling? Trade-offs? CEI consistency? Auditability? Or just awareness of common pitfalls?
How do you answer gas-optimization questions in a way that sounds like real engineering judgment instead of parroting a checklist?

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ChainMentorNaina

@ChainMentorNaina • 1mo

I’ve interviewed a bunch of juniors recently, and honestly the biggest giveaway is whether they treat gas like a formula or a decision. Most juniors talk in absolutes: “storage is expensive,” “memory is cheaper,” “avoid loops.” That’s fine, but everyone says that.

What seniors listen for is your sense of boundaries. Something like: “I only optimize when I know the function is called frequently enough for the gas savings to matter. Otherwise I keep clarity.” That one line alone signals maturity.

Also, mentioning risk matters more than the actual optimization: “I’m careful with tricky patterns that might hurt auditability or break CEI flow even if they save gas.” Seniors know juniors can’t profile like experts, but they want to see that you understand when optimization becomes dangerous.

Even referencing a small project where you measured SSTORE cost differences shows more thought than memorizing generic patterns.

DeFiArchitect

@DeFiArchitect • 2w

A framing that helped me a lot: talk about how you would investigate gas, not just apply gas tricks. Mentioning tools like forge test --gas-report or even saying “I check traces to identify hot paths” immediately tells the interviewer you think in steps.

In one interview I said: “Before optimizing, I want to see which functions dominate gas usage under expected workloads. Then I decide if caching or refactoring makes sense.” The senior told me later that this answer stood out because I focused on process, not trivia.

Another thing: tie your reasoning to intent. “If an optimization hides intent or makes invariants harder to validate, I’ll skip it.” This is something auditors repeat all the time — expensive clarity is cheaper than a subtle bug.

You don’t need production experience to give a strong answer. You need curiosity + trade-off thinking + an understanding that gas is part of secure design, not a leaderboard.

Andria Shines

@ChainSage • 2w

If you really want to stand out, mention testing impact: “Some optimizations break invariant tests or snapshot tests, so I check them after each change.” Shows you think beyond just code

Shubhada Pande

@ShubhadaJP • 2w

We’ve seen this pattern across AOB — juniors memorize gas tricks, seniors look for reasoning. If you want more examples of how engineers explain gas maturity, these discussions will help:

• Gas optimization panic — how much should juniors care? https://artofblockchain.club/discussion/gas-optimization-panic-how-much-should-juniors-care-during-interviews

• How do you quantify gas optimization success in QA? https://artofblockchain.club/discussion/how-do-you-quantify-gas-optimization-success-in-blockchain-qa-interviews

• Testing CEI patterns in real workflows https://artofblockchain.club/discussion/how-do-you-practically-test-cei-patterns-in-solidity-qa-workflows

Hope this helps someone preparing right now — this topic comes up in almost every dev interview.