Middle/Senior Backend 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, visitxsolla.com.

ABOUT YOU

We are looking for aMiddle/Senior Backend Engineer who ispassionate about building scalable blockchain infrastructure and Web3 services to join ourXsolla ZK team. The best candidate will be someone who thrives in a fast-paced, highly collaborative, and exceptionally dynamic setting and is excited todevelop backend systems that power NFT marketplaces, smart wallets, and blockchain-based gaming infrastructure.

Strongbackend development skills in Go are essential, along with experience inbuilding high-load distributed systems and working with databases. The ability todesign resilient microservices architecture and integrate with blockchain networks will be key to your success in this role.

If you're passionate aboutbuilding the infrastructure layer for next-generation gaming and loveworking on cutting-edge blockchain technology that enables gamers to truly own their digital assets, we would love to hear from you!

About the project

Xsolla ZK is building a cross-game infrastructure that empowers gamers to freely trade and use their digital assets without barriers. The backend team develops services for:

• • Xsolla Bazaar — NFT marketplace for trading digital assets across Ethereum, Polygon, and Xsolla ZK chains

  • Web3 Backpack — Smart wallet backend with account abstraction (ZK SSO 4337)

  • Blockchain Services — Event scanners, transaction processors, and Web3 connectors

  • BFF Layer — Backend-for-Frontend services orchestrating complex Web3 operations

  Tech Stack:

  • • Language: Go (go-ethereum, ethkit, idiomatic concurrency patterns)

    • Databases: MongoDB, PostgreSQL, Redis

    • Message Queue: NATS, RabbitMQ, Kafka

    • API: REST, WebSocket, gRPC, OpenAPI (Swagger)

    • Blockchain Infrastructure:

    • ZK Stack / ZKsync Era: EraVM, zksolc/zkvyper compilers, system contracts, bootloader, native Account Abstraction on zkSync-family chains

    • Account Abstraction (ERC-4337): EntryPoint (v0.6–v0.8), UserOperation lifecycle (prepare→sign→submit→confirm), bundler and paymaster roles, ERC-7562 validation rules, ERC-6492 signature validation for undeployed accounts

    • Ethereum L1: go-ethereum, abigen for smart contract bindings, RPC and indexer semantics

    • Smart Contracts: Solidity, ERC-20/721/1155, modular account standards (ERC-7579 / ERC-6900), session keys (ERC-7710 / ERC-7715)

    • Signature Schemes: EIP-712 typed data, ERC-1271 contract signatures, WebAuthn/passkey (P-256)

    • Infrastructure: Docker, Kubernetes, GitLab CI/CD, Graylog

    Key Technical Challenges:

    • • ZK Stack Integration: Working with EraVM execution environment, native Account Abstraction on zkSync-family chains, double resource accounting (EE gas + native computational resources), L1↔L2 communication via ZKsync Gateway, finality and reorg behavior

      • Account Abstraction Backend Services: Implementing the ERC-4337 UserOperation lifecycle, integrating with bundlers and paymasters, handling gas estimation failure modes and counterfactual deployment

      • Smart Contract Interaction: Generating Go bindings via abigen, handling factory dependencies for contract deployment, implementing EIP-712 transaction signing and ERC-1271 signature verification

      • Session Keys & Delegated Permissions: Supporting scoped, time-limited, contract-allowlisted authority (ERC-7710 / ERC-7715) for gasless, prompt-free gameplay transactions

      • Event Processing: Building blockchain event scanners for multiple chains (Ethereum, Polygon, Xsolla ZK), implementing reorg handling and transaction finality tracking

      • High-Availability Architecture: Designing resilient microservices for NFT marketplace and wallet backends with real-time WebSocket updates

Responsibilities

• • Develop backend services usingGo withethkit andgo-ethereum for Ethereum interactions and RPC integration

  • Integrate withZK Stack infrastructure: work with EraVM, system contracts, and L1↔L2 messaging

  • Build and maintainwallet backend indexing integrations for real-time token balance tracking and webhooks (via internal indexer or third-party providers)

  • Design and implement APIs for NFT marketplace and orderbook services, including on-chain order matching and settlement flows

  • Implementsmart contract interaction layer using abigen-generated Go bindings for ERC-20/721/1155 tokens

  • BuildAccount Abstraction (ERC-4337) backend support: UserOperation submission and monitoring, paymaster gas-sponsorship logic, session-key issuance and revocation

  • Develop blockchainevent scanners with reorg handling for Ethereum, Polygon, and Xsolla ZK chains

  • ImplementBFF (Backend-for-Frontend) services orchestrating complex multi-chain operations

  • Design efficientcaching and indexing strategies for on-chain data using Redis and MongoDB

  • Write comprehensive tests including integration tests with local ZKsync test environment

  • Document APIs using OpenAPI/Swagger specification

  • Monitor and troubleshoot production systems, handle blockchain-specific edge cases (stuck transactions, gas estimation)

Nice to Have

 

Required:

• • 2+ years of commercial experience withGo

  • Strong understanding ofMongoDB andPostgreSQL (query optimization, indexing)

  • Experience withRedis for caching and session management

  • Knowledge ofmessage queues (NATS, RabbitMQ, or similar)

  • Experience designing and implementingREST APIs with OpenAPI/Swagger

  • Understanding ofmicroservices architecture patterns

  • Experience withDocker and container orchestration basics

  • Proficiency withGit and GitLab CI/CD

  • Solid understanding ofdistributed systems concepts

  Preferred:

  • • Experience withEthereum/EVM blockchain integration:

    • Working with go-ethereum library and RPC nodes

    • Smart contract interaction via ABI bindings (abigen)

    • Understanding of transaction lifecycle, gas estimation, nonce management

    • Knowledge ofZK Stack / ZKsync Era:

    • EraVM execution model and differences from EVM, including native Account Abstraction on zkSync-family chains

    • System contracts (ContractDeployer, NonceHolder, etc.)

    • L1↔L2 communication, bridging, and finality/reorg behavior

    • Working knowledge ofERC-4337 Account Abstraction:

    • EntryPoint contract and the UserOperation lifecycle

    • Bundler and paymaster roles, gas estimation failure modes

    • Session keys and delegated permissions (ERC-7710 / ERC-7715)

    • Familiarity withsignature schemes: EIP-712 typed data, ERC-1271 contract signatures, WebAuthn/passkey signers

    • Exposure toAA infrastructure providers (any of: Sequence, thirdweb, Privy, Dynamic, Turnkey, Pimlico, Alchemy, Biconomy, ZeroDev, Safe{Core}) for wallet, indexer, or transaction-relay integrations

    • Knowledge oftoken standards (ERC-20, ERC-721, ERC-1155) and their implementation details

    • Experience withblockchain event processing: event scanning, reorg handling, finality

    • Understanding ofDeFi concepts and NFT marketplace mechanics

    • Experience withKubernetes for container orchestration

BENEFITS

We are passionate about fostering a supportive environment for our team, so we prioritize the physical, mental, and emotional well-being of our employees and their families through a comprehensive Benefits Program. This includes medical, dental, and vision, PTO, and a personalized career roadmap for each employee. By investing in professional development through training and educational opportunities, we ensure that our team thrives both personally and professionally. Together, we’re not just building a business; we’re cultivating a community that values creativity, collaboration, and the transformative power of play. 

EMPLOYMENT DETAILS

• Location: Remote (worldwide)

• Employment Type: Full-time

• Schedule: 10:00–19:00 (flexible)

• Contract: Employment agreement (entity or EOR arranged per candidate location)

EQUAL EMPLOYMENT STATEMENT

Xsolla is dedicated to creating a diverse environment and is proud to be an equal-opportunity employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, gender, language, sexual orientation, national origin, genetics, political beliefs, disability, age, marital status, social background or other characteristics.

We are committed to compliance with all fair employment practices regarding citizenship and immigration status.

CONTACT

If you have questions regarding our hiring practices, please contact careers@xsolla.com.

For more vacancies, visit:xsolla.com/careers