Senior Fullstack Engineer

ABOUT US Xsolla is a global commerce company with robust tools and services to help developers solve the inherent challenges of the video game industry. From indie to AAA, companies partner with Xsolla to help them fund, distribute, market, and monetize their games. Grounded in the belief in the future of video games, Xsolla is resolute in the mission to bring opportunities together, and continually make new resources available to creators. Headquartered and incorporated in Los Angeles, California, Xsolla operates as the merchant of record and has helped over 1,500+ game developers to reach more players and grow their businesses around the world. With more paths to profits and ways to win, developers have all the things needed to enjoy the game. For more information, visit xsolla.com .

Xsolla ZK is building a cross-game infrastructure that empowers gamers to freely trade and use their digital assets without barriers. As a Fullstack Engineer, you'll work across the entire stack: Products: Xsolla Bazaar — NFT marketplace for trading digital assets Web3 Backpack — Smart wallet with account abstraction Web3 SDKs — Developer toolkits for blockchain integration Admin Panels — Internal tools for managing Web3 operations Tech Stack: Backend: Language: Go (go-ethereum, ethkit) Databases: MongoDB, PostgreSQL, Redis API: REST, WebSocket, gRPC, OpenAPI (Swagger) Message Queue: NATS, RabbitMQ, Kafka Blockchain Infrastructure: ZK Stack / ZKsync Era (EraVM, system contracts, native Account Abstraction) Account Abstraction (ERC-4337): EntryPoint, UserOperation lifecycle, bundlers, paymasters Ethereum L1 integration, abigen contract bindings Frontend: Languages: JavaScript (ES6+), TypeScript Frameworks: React, Next.js, React Native State Management: RTK, Zustand Styling: Tailwind CSS, Tamagui, CSS-in-JS Web3 Libraries & Standards: Wallet provider standards: EIP-1193, EIP-6963 (multi-wallet discovery), EIP-5792 (batched calls) ethers.js, viem for Ethereum interactions wagmi for React hooks WalletConnect for multi-wallet support Embedded/AA wallet SDK (e.g. Sequence, thirdweb, Privy, Dynamic, or equivalent) for social-login smart accounts Infrastructure: DevOps: Docker, Kubernetes, GitLab CI/CD Monitoring: Graylog, Prometheus Key Technical Challenges: Full-Stack Web3 Features: Building end-to-end flows from smart contract events to real-time UI updates Account Abstraction Integration: Implementing embedded/smart-account wallets with social auth, ERC-4337 UserOperation flows, and gasless transactions via paymasters ZK Stack Backend: Working with EraVM differences, native Account Abstraction on zkSync-family chains, handling L1↔L2 bridging operations Signature & Session Handling: Implementing EIP-712 signing, ERC-1271 verification, and session-key-scoped permissions for in-game transactions Cross-Platform Consistency: Sharing business logic between web and mobile using React/React Native

Backend Development: Develop backend services in Go using go-ethereum / ethkit for wallet operations and blockchain interactions Implement and monitor the ERC-4337 UserOperation lifecycle (prepare→sign→submit→confirm) against bundlers and paymasters Implement smart contract interaction layer with abigen -generated Go bindings Build Account Abstraction support: paymaster gas-sponsorship logic, session-key issuance (ERC-7710 / ERC-7715) for gameplay transactions Design BFF services orchestrating data from multiple blockchain sources, indexers, and wallet infrastructure providers Frontend Development: Build responsive applications using React/Next.js integrated with an embedded/AA wallet SDK Implement Embedded Wallet flows: social auth (Google, Apple), email login, passkey (WebAuthn/P-256) support Create Web3-enabled UIs using wagmi hooks and viem for contract reads/writes, following EIP-1193/EIP-6963 provider standards Implement transaction confirmation flows that clearly convey what the player is approving (EIP-712 typed-data signing) Develop real-time features with WebSocket subscriptions for blockchain events Build cross-platform components with Tamagui for web and React Native Full-Stack Integration: Design and implement complete features from smart contract events to UI updates Handle ZK Stack specifics : EraVM gas model differences, native Account Abstraction, L1↔L2 bridging UI flows Implement transaction tracking : status polling, reorg handling, user notifications Create admin panels for managing NFT drops, marketplace settings, and analytics Write comprehensive tests for both backend (Go) and frontend (Jest, React Testing Library) Document APIs using OpenAPI/Swagger and maintain technical documentation

Required: Backend Skills: 3+ years of commercial experience with Go Strong knowledge of REST API design and implementation Experience with MongoDB and/or PostgreSQL Understanding of microservices architecture Frontend Skills: 3+ years of experience with React and modern JavaScript/TypeScript Proficiency in state management solutions (Redux, Zustand, etc.) Experience with responsive design and CSS frameworks Understanding of web performance optimization General: Experience with Git and CI/CD pipelines Familiarity with Docker and containerization Strong problem-solving and communication skills Preferred: Web3 & Blockchain: Working knowledge of ERC-4337 Account Abstraction : EntryPoint, UserOperation lifecycle, bundler/paymaster roles Understanding of session keys and delegated permissions (ERC-7710 / ERC-7715) and signature schemes (EIP-712, ERC-1271, WebAuthn/passkey) Familiarity with wallet provider standards : EIP-1193, EIP-6963, EIP-5792 Exposure to an embedded/AA wallet SDK (Sequence, thirdweb, Privy, Dynamic, Turnkey, or equivalent): Embedded Wallet integration (social auth, passkeys) Indexer/data-availability integration for balance/activity tracking Gas-sponsorship / transaction-relay APIs Knowledge of ZK Stack / ZKsync Era : Understanding of EraVM vs EVM differences L1↔L2 communication patterns Native Account Abstraction on zkSync-family chains Experience with ethers.js , viem , and wagmi for React Understanding of smart contract interaction : ABI, events, transaction lifecycle Knowledge of token standards (ERC-20, ERC-721, ERC-1155) Additional: Experience with Next.js SSR/SSG and App Router Familiarity with React Native and Tamagui for cross-platform Understanding of WebSocket for real-time blockchain events Knowledge of Kubernetes and cloud infrastructure

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