Senior Backend Engineer, Onchain

ABOUT POLYMARKET Polymarket is the world's largest prediction market platform. We enable individuals to express views on real-world events by trading on outcomes across politics, economics, sports, culture, and current affairs. Built as a peer-to-peer marketplace with no centralized "house," Polymarket aggregates diverse opinions into transparent, market-based probabilities that reflect collective expectations about the future. We're growing fast — both in terms of volume ($21B traded in 2025) and adoption as an alternative news source. Our ambition is to become a ubiquitous beacon of truth in global media and we need your help adding fuel to the fire. ABOUT THE ROLE Polymarket is looking for a world-class backend engineer with deep blockchain knowledge to join our Onchain Execution team. This team owns the systems that sit between Polymarket's product and the chain — the relayers, transaction pipelines, RPC infrastructure, and settlement logic that make every trade possible. You'll be working on technically demanding problems at the intersection of distributed systems, blockchain protocols, and high-throughput backend engineering. The ideal candidate brings both fundamentals (clean code, solid databases, well-designed APIs) and fluency in how EVM networks actually work under the hood. If you've built or maintained relayer systems, worked on scalable RPC infrastructure, or contributed to core blockchain node software, this role is a strong match. WHAT YOU'LL DO - Build and maintain onchain execution infrastructure. Design and operate the relayer systems, transaction pipelines, and settlement logic that power Polymarket's markets end-to-end. - Architect high-performance backend systems. Build reliable, scalable APIs and services that handle high transaction volumes and real-time data with low latency. - Own RPC and chain connectivity. Implement and scale the endpoints and integrations that keep Polymarket reliably connected to EVM networks. - Optimize performance and reliability. Push the limits of throughput and efficiency across our onchain systems, ensuring seamless operation as volume grows. - Enhance security and fault tolerance. Apply best practices for secure, highly available distributed systems — especially in adversarial onchain environments. - Contribute to code quality. Participate actively in code reviews and help maintain a high engineering bar across the team. - Stay close to the frontier. Track developments across EVM ecosystems and blockchain infrastructure, and bring relevant innovations back to Polymarket's stack. WHAT WE'RE LOOKING FOR - 5+ years of experience in backend development - Strong fundamentals: clean, well-tested code; solid database design (PostgreSQL or equivalent); well-structured APIs - Solid understanding of how EVM networks work: transaction lifecycle, gas mechanics, mempool dynamics, smart contract interactions - Experience with systems-level languages: Golang is strongly preferred; Rust or C++ also valued - Familiarity with blockchain infrastructure: RPC nodes, event indexing, relayer architectures, or similar - Excellent problem-solving skills and the ability to work through ambiguous, high-stakes technical challenges - (Plus) Direct experience building or operating a relayer system - (Plus) Experience with Ethereum rollup technologies (Arbitrum Nova, Optimism, etc.) - (Plus) Experience with BFT consensus engines, libp2p, or core node software - (Plus) Open source contributor in the blockchain ecosystem - (Plus) Active on ethresear.ch http://ethresear.ch or similar protocol research forums BENEFITS - Competitive salary & equity - Unlimited PTO - Full Health, Vision, & Dental coverage - 401k match - Hardware setup: new MacBook Pro, big display, & accessories