• Difficulty - Medium
    Total Plays - 13
    Allowed Time - 10 sec
    Best time - 1.846

    Why is storing large arrays on-chain discouraged?

    Tip: Click "Play" to reveal options and start playing.

    #A
    #B
    #C
    #D
    Explanation:
    Storage is the most expensive resource in the EVM. Large arrays result in high operational cost and poor long-term scalability.
  • Difficulty - Medium
    Total Plays - 13
    Allowed Time - 10 sec
    Best time - 0.675

    Why is using block.timestamp in fairness-critical logic dangerous?

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    #A
    #B
    #C
    #D
    Explanation:
    Miners can adjust timestamps within a reasonable range, enabling subtle manipulation. This can affect auctions, lotteries, and reward systems
  • Job Expired
    C

    Senior Analytics Engineer

    ConsensysFull TimeNA

    Remote Posted: Nov 26, 2025
    Job description
    This role supports Consensys’s Data team, responsible for transforming raw data into reliable, analysis-ready models that power KPIs across Finance, Product, and Leadership. As a Senior Analytics Engineer, you will design, build, document, and maintain data models and semantic layers, while ensuring accuracy, governance, and consistency across the organization. You...
  • Job Expired
    C

    Backend Engineer — MetaMask (API Platform)

    ConsensusFull TimeNA

    Remote (United States, Canada, LATAM, EMEA) Posted: Nov 26, 2025
    Job description
    This role supports MetaMask’s API Platform team, which builds backend services powering key product experiences across MetaMask clients. As a Backend Engineer, you will develop Node.js services that support APIs such as Price, Token, Account, and NFT, contributing to reliable and scalable infrastructure used by millions of users. The position...
  • Job Expired
    C

    Release Engineer — MetaMask

    ConsensysFull TimeNA

    Remote (Canada, EMEA, LATAM, United States) Posted: Nov 26, 2025
    Job description
    This role supports MetaMask’s mobile and browser extension teams by ensuring smooth, consistent, and high-quality application releases. As a Release Engineer, you will manage daily release operations, validate builds, automate workflows, and oversee CI/CD pipelines across multiple platforms. The position involves coordinating with engineering, QA, and product teams to maintain...
  • Job Expired
    C

    Senior Solutions Architect

    ChainalysisFull TimeNA

    Remote Posted: Nov 26, 2025
    Job description
    Chainalysis develops blockchain data tools used by government agencies, financial institutions, and organizations to understand on-chain activity. The Senior Solutions Architect role sits within the Solutions Architecture function and supports the sales cycle by translating customer objectives into technical paths for implementation. This position requires a strong understanding of Chainalysis’...
  • Difficulty - Medium
    Total Plays - 7
    Allowed Time - 10 sec
    Best time - 3.010

    5. Why is delegatecall risky?

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    #A
    #B
    #C
    #D
    Explanation:
    delegatecall executes callee code in the caller’s storage context, leading to storage collisions and privilege escalation. This is a key attack vector in proxy contracts.
  • Difficulty - Medium
    Total Plays - 6
    Allowed Time - 10 sec
    Best time - 10

    4. Which opcode is responsible for dynamic memory expansion cost?

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    #A
    #B
    #C
    #D
    Explanation:
    MSTORE triggers memory expansion when writing to higher memory slots. Memory grows quadratically, so developers must understand how loops and large arrays impact gas.
  • Difficulty - Medium
    Total Plays - 8
    Allowed Time - 10 sec
    Best time - 4.033

    What happens if a constructor of a deployed contract reverts?

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    #A
    #B
    #C
    #D
    Explanation:
    If the constructor reverts, the entire deployment fails and no contract is created. This prevents partially-initialized smart contracts from being pushed on-chain
  • Difficulty - Medium
    Total Plays - 5
    Allowed Time - 10 sec
    Best time - 4.975

    1. What does EXTCODEHASH primarily help detect?

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    #A
    #B
    #C
    #D
    Explanation:
    EXTCODEHASH returns the hash of a contract’s deployed bytecode, allowing detection of code changes or empty accounts. Auditors use it to verify contract identity and defend against unexpected contract replacement patterns
  • Difficulty - Medium
    Total Plays - 8
    Allowed Time - 10 sec
    Best time - 5.082

    What is the main security benefit of using immutable variables?

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    #A
    #B
    #C
    #D
    Explanation:
    immutable variables are stored directly in bytecode, not in storage, reducing runtime gas and preventing accidental overwrites. It is a common optimization technique in gas-efficient contract design.
  • Job Expired
    L

    Senior SDET

    LedgerFull TimeNA

    London, United Kingdom (Hybrid) Posted: Nov 24, 2025
    Job description
    Ledger is hiring a Senior SDET to support quality assurance across its digital asset and Web3 product environment by enabling automation, improving testing methodologies, and enhancing CI/CD reliability. This role involves designing automation tools, creating test frameworks, and working closely with product teams to embed test ownership into development workflows....
  • Job Expired
    E

    Staff Solana Engineer

    ExodusFull TimeNA

    Remote Posted: Nov 24, 2025
    Job description
    Exodus is seeking a Staff Solana Engineer to lead and maintain all Solana-related components across its wallet ecosystem. The role focuses on enhancing Solana wallet functionality, refining smart contract support, and delivering stable and optimized integrations for end users. This position requires deep fluency in Solana architecture, with ownership over...
  • Job Expired
    E

    Senior Software Engineer

    ExodusFull TimeNA

    Remote Posted: Nov 22, 2025
    Job description
    Exodus is hiring Senior Software Engineers to support multiple engineering initiatives across its wallet and exchange products. The role involves contributing to front-end and back-end development, improving performance across applications, enhancing the wallet SDK, and helping refine developer tooling. You will collaborate closely with engineers and product managers to deliver...
  • Job Expired
    B

    Cyber Security Analyst

    Blockchain.comFull TimeNA

    London Posted: Nov 22, 2025
    Job description
    Blockchain.com is seeking a Cyber Security Analyst to support its security operations as the company continues scaling its global digital asset platform. The role involves working within the internal security team to safeguard systems, employees, and users across a distributed financial environment. This includes monitoring threats, managing endpoint protection, responding...