Senior Fullstack Engineer

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Description

About the project - 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 Responsibilities - 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 Nice to Have - 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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