Spark.Fi - Smart Contract

deCircle•New York, NY

About The Position

Spark is building a scalable on-chain capital allocation engine for DeFi, designed to efficiently move billions in liquidity across lending markets, yield strategies, and liquidity venues. As the DeFi ecosystem matures, the focus shifts to intelligent capital deployment, sustainable yield generation, and large-scale liquidity management across fragmented markets. Spark aims to be at the center of this evolution. This role is for a Senior Smart Contract Engineer to help architect and build the core primitives for Spark’s vault infrastructure, AMM integrations, and yield-generating systems. It's a deeply technical position focused on designing secure, capital-efficient smart contract systems that interact with various DeFi protocols and frameworks. The ideal candidate understands that modern DeFi infrastructure is a liquidity coordination problem and is comfortable with concepts like capital movement between protocols, yield generation and distribution, user-facing vault complexity, and liquidity mechanism behavior under real market conditions.

Requirements

Several years of experience building production-grade smart contracts.
Experience with systems involving vaults, lending markets, AMMs, liquidity routing, staking or yield systems, or broader DeFi infrastructure.
Comfortable owning systems end-to-end: architecture discussions, protocol design, implementation, testing, optimization, and audit preparation.
Experience with Solidity.
Experience with Foundry / Hardhat.
Experience with ERC-4626 vault standards.
Experience with AMM mechanics and LP accounting.
Experience with yield aggregation systems.
Experience with Oracle integrations.
Experience with upgradeable contract architectures.
Knowledge of gas optimization and security best practices.
Understanding of the economic behavior behind the code, including liquidity behavior under volatility, yield incentive impact on user behavior, AMM impact on capital efficiency, vault architecture optimization, and protocol design influence on systemic risk.
Understanding of capital efficiency, liquidity flows, incentive alignment, composability, and protocol-level risk.

Nice To Haves

Experience working on live protocols with meaningful TVL.
Experience operating systems exposed to real liquidity conditions and adversarial environments.

Responsibilities

Architect and build core primitives for Spark’s vault infrastructure, AMM integrations, and yield-generating systems.
Design secure, capital-efficient smart contract systems interacting with lending protocols, liquidity pools, and automated strategy frameworks.
Develop ERC-4626 vault architectures.
Build yield allocation and rebalancing systems.
Integrate with AMMs and liquidity pools.
Create automated capital deployment frameworks.
Develop treasury and liquidity management infrastructure.
Implement reward distribution and fee accounting systems.
Design strategy execution and risk-aware routing mechanisms.
Build systems that abstract complexity while remaining transparent, composable, and secure.
Contribute to infrastructure for managing large-scale on-chain liquidity and enabling efficient access to yield.
Collaborate with protocol engineers, treasury and risk contributors, and product stakeholders to design scalable and composable systems within the Ethereum ecosystem.