Software Engineer

Xsolla is hiring a Software Engineer, Web3, for Xsolla ZK, its zkSync-based Web3 ecosystem. The senior full-stack role builds and operates backend services, dApp frontends, SDKs, and smart-contract integrations, with responsibility for end-to-end features, architecture, security, and production support.

Responsibilities:

• Features end to end: backend, frontend and production
• The on-chain / off-chain architecture of your product: what lives in contracts, what lives in services, and how the two stay consistent. You make these decisions and justify them in writing
• Security and correctness of what you ship: signing flows, interactions with contracts that hold user assets, keys and secrets
• Production operation of your services, as part of the team's on-call rotation
• Build backend services in Go and TypeScript: chain indexing, transaction relaying, event processing, APIs for dApps and SDKs
• Build infrastructure backend services for tokenizing in-game items and currencies
• Build dApp frontends in React: wallet connection, transaction signing, on-chain state in the UI
• Integrate smart wallets into products: accounts, paymasters, bundlers
• Develop SDKs used by game studios and partners
• Monitor services and contracts in production and take part in on-call
• Review code
• Set up and maintain AI tooling in the repositories (Claude Code, Codex, Cursor: rules, context, harness) so the team uses it effectively

Requirements:

• 5+ years of commercial software development, with senior-level production experience across backend and frontend
• dApps that you shipped to production and maintained
• viem and wagmi in production: clients and transports, contract reads and writes with typed ABIs, event subscriptions, wagmi hooks and connectors, caching and invalidation of on-chain state
• How wallet signers work: EOAs, browser and embedded wallets, smart accounts; personal_sign (EIP-191) and typed data (EIP-712); the EIP-1193 provider; network switching
• Hands-on experience with smart wallets: UserOperations, gas sponsored via paymasters, signature validation for contract accounts (ERC-1271)
• Go and TypeScript (Node.js) for production services
• Processing on-chain events: idempotency, reorg handling, retries
• Asynchronous messaging and event-driven design (Kafka, RabbitMQ or NATS): delivery guarantees, ordering, reprocessing
• Relational databases (PostgreSQL) and caching (Redis)
• Designing REST and gRPC APIs: versioning, backward compatibility
• React and TypeScript: rendering model, state management, performance
• Web security fundamentals: XSS, CSRF, CSP, safe handling of signatures and keys in the browser
• Reading and understanding Solidity contracts and the EVM (storage, gas, call semantics, proxy upgrade patterns, access control) well enough to integrate with them safely and review changes
• Common contract vulnerability classes (reentrancy, front-running / MEV, oracle manipulation, signature replay) and how they affect the off-chain side
• Containers and orchestration (Docker, Kubernetes) at the level of deploying and debugging your own services
• Observability (we use Datadog; experience with Prometheus, Grafana, ELK / Graylog or OpenTelemetry also counts): metrics, logs, tracing and alerting for services and contracts; diagnosing incidents in production
• Testing: unit, integration, E2E
• Git, CI/CD (GitLab CI or similar)
• Daily hands-on use of AI coding tools (Claude Code, Codex, Cursor) for development and review, including configuring them for a repository
• Spoken English at B2 level or higher
• zkSync / ZK Stack and the specifics of the zk-rollup stack
• Designing, writing and testing smart contracts in Solidity with Foundry; deploying and upgrading them safely
• Building ERC-4337 infrastructure yourself (bundlers, paymasters); EIP-6963, EIP-5792
• DeFi: DEX and AMM mechanics
• NFTs and marketplaces: ERC-721, ERC-1155, auction mechanics
• L2 infrastructure: running nodes, indexers, bridges
• Designing SDKs for external developers
• Gaming domain experience