Software Engineer

We are hiring a Software Engineer, Web3 for Xsolla ZK, Xsolla's Web3 ecosystem on a zkSync-based L2. It includes:

• smart wallets built on account abstraction;

• SDKs that game studios and partners use to bring players on-chain;

• infrastructure backend services for tokenizing in-game items and currencies;

• ecosystem dApps: a DEX, an NFT marketplace and an auction.

This is a senior fullstack role: you work across backend, frontend and smart contracts.

WHAT YOU WILL OWN

• 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

WHAT YOU WILL DO

• 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

Experience

• 5+ years of commercial software development, with senior-level production experience across backend and frontend

• dApps that you shipped to production and maintained

Web3 libraries and wallets

• 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)

Backend

• 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

Frontend

• React and TypeScript: rendering model, state management, performance

• Web security fundamentals: XSS, CSRF, CSP, safe handling of signatures and keys in the browser

Smart contracts

• 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

Operations

• 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

Engineering practices

• Testing: unit, integration, E2E

• Git, CI/CD (GitLab CI or similar)

AI-assisted engineering

• Daily hands-on use of AI coding tools (Claude Code, Codex, Cursor) for development and review, including configuring them for a repository

English

• 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