• Job Expired
    O

    Site Reliability Engineer

    Offchain LabsFull TimeNA

    Remote US Posted: Dec 4, 2025
    Job description
    Offchain Labs is seeking a Site Reliability Engineer to support and scale infrastructure powering the Arbitrum ecosystem. The role focuses on maintaining Kubernetes-based deployments, automating infrastructure using declarative tooling such as Terraform, and working within GitOps workflows using tools like ArgoCD. The candidate will diagnose complex reliability issues across distributed...
  • Job Expired
    O

    Security Engineer

    Offchain LabsFull TimeNA

    Remote Global Posted: Dec 4, 2025
    Job description
    Offchain Labs, the team behind the Arbitrum scaling ecosystem, is hiring a Security Engineer focused on securing cloud and blockchain infrastructure. The role involves working across AWS-based environments, Kubernetes, multi-region access systems, VPN-based security, and secrets management tools such as Vault or KMS. This position will support architecture analysis, threat...
  • Job Expired
    A

    Staff Backend Engineer

    Ava LabsFull TimeNA

    Brooklyn, NY or Remote (North America) Posted: Dec 4, 2025
    Job description
    Ava Labs is hiring a Staff Backend Engineer for their Institutional Custody division, focused on designing and scaling secure blockchain and wallet infrastructure. This role sits at the intersection of technical leadership and hands-on engineering, leading long-term architectural direction and backend development using Golang. The position works closely with cross-functional...
  • Job Expired
    T
    Remote Global Posted: Dec 3, 2025
    Job description
    This internship is intended for MSc/PhD students interested in contributing to research and engineering in large-scale AI model development at Tether. The role involves participation in building and improving SOTA models in domains such as LLMs, video models, and multimodal architectures. Interns will also work on enhancing distributed training infrastructure...
  • Job Expired
    A

    ZK Proof Engineer

    AxiomFull TimeNA

    New York (preferred) or Remote Posted: Dec 3, 2025
    Job description
    This role focuses on implementing and optimizing cryptographic systems related to zero-knowledge proof generation. Axiom develops verifiable and privacy-preserving software components, including the OpenVM zkVM framework, which supports flexible verification of program execution. The ZK Proof Engineer will contribute to building and refining ZK-enable infrastructure, integrating low-level computing, compiler frameworks,...
  • Job Expired
    N

    Internship

    NethermindFull TimeNA

    Remote Posted: Dec 3, 2025
    Job description
    This open application internship is offered by Nethermind for individuals interested in contributing to blockchain, Ethereum infrastructure, Web3 technologies, cryptography, research, and related fields. Applicants may come from various technical or analytical backgrounds and will have the opportunity to collaborate with distributed teams on research, engineering, infrastructure, or product-focused work.The...
  • Difficulty - Medium
    Total Plays - 13
    Allowed Time - 10 sec
    Best time - 4.554

    What makes nested delegatecalls dangerous?

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

    #A
    #B
    #C
    #D
    Explanation:
    Each delegatecall runs in the caller’s storage space, so nesting them multiplies the chances of overwriting incorrect slots. This breaks upgradeability guarantees and corrupts state. Auditors treat deep delegatecall chains as red flags.
  • Difficulty - Medium
    Total Plays - 16
    Allowed Time - 10 sec
    Best time - 2.746

    Why do upgradeable contracts avoid constructors?

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

    #A
    #B
    #C
    #D
    Explanation:
    Constructors run only during deployment and do not execute through proxies. Using an initializer ensures state is properly set through proxy calls. The entire proxy pattern relies on replacing constructors with explicit initialization.
  • Difficulty - Medium
    Total Plays - 20
    Allowed Time - 10 sec
    Best time - 1.062

    Why avoid multiple SSTOREs in a function?

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

    #A
    #B
    #C
    #D
    Explanation:
    SSTORE is one of the most expensive operations and repeating it unnecessarily multiplies costs. Caching values into memory and writing once dramatically optimizes gas. This is foundational in gas-sensitive protocols.
  • Difficulty - Medium
    Total Plays - 17
    Allowed Time - 10 sec
    Best time - 1.746

    Why is assert() dangerous in production?

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

    #A
    #B
    #C
    #D
    Explanation:
    assert() triggers a Panic error and is intended only for internal guarantees. If it fires in production, it indicates a compiler or logic bug. Developers should use require() for user-facing validation.
  • Difficulty - Medium
    Total Plays - 12
    Allowed Time - 10 sec
    Best time - 6.381

    What does a selector collision indicate?

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

    #A
    #B
    #C
    #D
    Explanation:
    Selector collisions occur when different function signatures hash to the same first 4 bytes. This leads to unintended dispatching and silent bugs. It’s especially dangerous in diamond proxies and minimal routers.
  • Difficulty - Medium
    Total Plays - 16
    Allowed Time - 10 sec
    Best time - 1.487

    Why is msg.value validation kept at the top of functions?

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

    #A
    #B
    #C
    #D
    Explanation:
    Validating msg.value early ensures no state mutation occurs before detecting invalid ether transfers. This prevents partially updated storage on failure, preserving atomicity. It aligns with checks-effects-interactions
  • Job Expired
    P

    Senior Software Engineer, Frontend

    PhantomFull TimeNA

    Remote Posted: Dec 1, 2025
    Job description
    This role focuses on frontend engineering for Phantom’s multi-chain self-custodial crypto wallet. The engineer will be responsible for building and enhancing user-facing features across the Phantom browser extension and website, contributing to UI performance, responsiveness, and quality. The position includes driving product enhancements that expand blockchain support, improving cross-chain usability,...
  • Job Expired
    P

    Senior Software Engineer, Full-Stack

    PhantomFull TimeNA

    Remote Posted: Dec 1, 2025
    Job description
    This role contributes to the engineering of Phantom’s multi-chain self-custodial wallet, enabling users to interact with crypto assets across Solana, Ethereum, Polygon, and Bitcoin. The position is full-stack, encompassing both user-facing interfaces and backend development, including APIs and service infrastructure that connects blockchain data to frontend experiences. The engineer will...
  • Difficulty - Medium
    Total Plays - 8
    Allowed Time - 10 sec
    Best time - 1.153

    What makes fallback functions error-prone?

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

    #A
    #B
    #C
    #D
    Explanation:
    Fallbacks receive raw calldata without predefined structure, forcing developers to manually decode and validate inputs. Any mistake leads to reentrancy or mis-routing. They must be extremely minimal.