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Difficulty - Medium

Total Plays - 8

Allowed Time - 10 sec

Best time - 1.367 sec

Which opcode differentiates EOAs from contracts?

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Explanation:
EXTCODESIZE returns zero for EOAs and non-zero for deployed contracts. This distinction is commonly used for contract detection, though it has edge cases.

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Aditi R

@aGoKU4J • 1w

How Do I Switch From UI/UX Design to a Blockchain or Web3 Career?

Has anyone here transitioned from regular UI/UX design into blockchain or Web3? I have three years of experience working on SaaS and web apps, but now I am curious about...

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Difficulty - Medium

Total Plays - 8

Allowed Time - 10 sec

Best time - 3.221 sec

Which opcode returns remaining gas?

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Explanation:
GASLEFT returns the amount of gas remaining in the current execution context. It is commonly used for gas-aware logic and debugging.

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Difficulty - Medium

Total Plays - 10

Allowed Time - 10 sec

Best time - 10 sec

Which type consumes exactly one storage slot regardless of value?

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Explanation:
bytes32 always occupies a full 32-byte storage slot. Smaller types may be packed together, but bytes32 always stands alone.

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Shubhada Pande

@ShubhadaJP • 1w

Proof-Based Hiring in Web3

Hiring in Web3 fails when teams rely on familiar signals instead of predictive ones.This hub collects AOB articles and discussions that focus on evidence-driven hiring — how candidates debug, reason,...

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Difficulty - Medium

Total Plays - 8

Allowed Time - 10 sec

Best time - 2.477 sec

Why does storage write order matter for structs?

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Explanation:
Solidity packs struct variables tightly into storage slots based on declaration order. Reordering fields can change slot boundaries and break upgrade compatibility.

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FintechLee

@FintechLee • 1w

Getting Paid in Stablecoins in Web3: Salary, Tax, and Risk — How Do Professionals Actually Handle It?

I’m seeing more Web3 and crypto companies offer salaries fully or partially in stablecoins like USDT or USDC, especially for remote roles. On paper, it sounds convenient — faster payments,...

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Shubhada Pande

@ShubhadaJP • 1w

Zero-Knowledge Proofs & Cryptography Hub: Understanding ZK Systems, Privacy Engineering & Real-World Protocol Design

Zero-knowledge proofs (ZKPs) are no longer just academic cryptography. They now power real systems — from rollups and privacy chains to identity layers, proof-of-reserves, and scalable computation.This hub brings together...

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Difficulty - Medium

Total Plays - 7

Allowed Time - 10 sec

Best time - 5.388 sec

What determines the base slot of a mapping?

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Explanation:
The base slot of a mapping is derived using keccak256(key . slot). This hashing ensures unique storage locations per key without collisions.

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CryptoSagePriya

@CryptoSagePriya • 1w

I’m starting my first smart contract job next week and I’m honestly nervous — what actually matters during probation?

I’m starting my first smart contract job next week and honestly I’m nervous.Everyone keeps saying “probation decides everything” but no one really explains how.Some people say move fast. Some say...

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Damon Whitney

@CareerSensei • 1w

What junior blockchain developer portfolio projects actually impress hiring managers?

Got a comp sci background and did some web dev work with JavaScript, React, and Node.js. Recently been hyper-focused on blockchain development—messing around with Ethereum, smart contract development, and Solidity...

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Difficulty - Medium

Total Plays - 5

Allowed Time - 10 sec

Best time - 10 sec

Which operation causes storage slot re-packing?

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Explanation:
Changing variable types alters how Solidity packs them into storage slots. This can shift offsets and corrupt existing storage layouts in upgradeable contracts.

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Difficulty - Medium

Total Plays - 10

Allowed Time - 10 sec

Best time - 1.638 sec

Which data location is read-only by default?

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Explanation:
Calldata is immutable and cannot be modified by the callee. This makes it gas-efficient and safe for external function inputs

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Difficulty - Medium

Total Plays - 6

Allowed Time - 10 sec

Best time - 3.221 sec

What happens to storage slots after contract self-destruct?

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Explanation:
Storage is not automatically wiped when a contract self-destructs. The data remains on-chain and can be accessed again if a contract is redeployed at the same address.

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Difficulty - Medium

Total Plays - 12

Allowed Time - 10 sec

Best time - 1.748 sec

Why is bytes32 cheaper than string in storage?

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Explanation:
bytes32 has a fixed 32-byte size and fits into a single storage slot. string is dynamically sized and requires additional storage pointers and length metadata.

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