Senior Fullstack Engineer

Fullstack Engineer

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:

• 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
• 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
• Experience with Git and CI/CD pipelines
• Familiarity with Docker and containerization
• Strong problem-solving and communication skills

Preferred:

• 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)
• 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