Middle/Senior Backend Engineer

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Description

About the project - Xsolla ID is a strategic core service — the centralized identity provider for the entire Xsolla ecosystem. It is not just a login form; it's a comprehensive IAM platform enabling authentication and authorization across all B2C products, including Xsolla Wallet, Xsolla App, Web Shops, and partner integrations. Tech Stack: Language: Go (idiomatic code, concurrency patterns, performance profiling) - Databases: PostgreSQL (schema design, query optimization, migrations at scale), MySQL, Redis - Distributed SQL: CockroachDB (multi-region deployments, clock skew handling, survivability trade-offs) for geo-distributed data residency - Message Streaming: NATS, Kafka (event-driven patterns, consumer groups, at-least-once delivery), RabbitMQ - Infrastructure: Docker, Kubernetes, Nginx - Identity Stack: Ory ecosystem (Hydra for OAuth2/OIDC, Kratos for identity management) with a custom Auth API orchestrator and plugin architecture - Protocols: OAuth 2.0 / OIDC (authorization code + PKCE, client credentials, device flow, token introspection, refresh strategies), WebAuthn - Web Security: cookie security, CSRF, XSS protection, secure token storage, TLS, secure session management - Architecture: Microservices, High Availability design - Key Technical Challenges: Building Web2 & Web3 authentication flows (OTP, passkeys, biometrics, wallet-based login) - Implementing custom auth methods without forking Ory - SSO without third-party cookies - Zero-downtime migration from legacy Xsolla Login with bidirectional identity sync - Geo-distributed data residency via CockroachDB - High availability and scaling for millions of concurrent users - SDK development and integration with multiple Xsolla products Responsibilities - Develop and maintain backend services for the Xsolla ID platform using Go - Design and implement OAuth 2.0 / OIDC flows (authorization code + PKCE, client credentials, device flow), token introspection, and refresh strategies - Work with the Ory ecosystem (Hydra, Kratos) and extend the custom Auth API orchestrator and plugin architecture - Apply web security fundamentals: cookie security, CSRF/XSS protection, secure token storage, TLS, secure session management - Optimize database queries and ensure high performance under heavy loads (PostgreSQL, MySQL, Redis, CockroachDB) - Build and maintain microservices architecture with focus on reliability and scalability - Contribute to zero-downtime migration from legacy Xsolla Login with bidirectional identity sync - Write clean, well-tested code with comprehensive unit and integration test coverage - Collaborate with frontend engineers on SDK and widget integration - Participate in code reviews and contribute to technical documentation - Support production systems and troubleshoot issues across the authentication stack - QUALIFICATIONS Required: 2+ years of commercial experience with Go - Strong understanding of PostgreSQL and Redis (query optimization, indexing strategies) - Working knowledge of OAuth 2.0 / OIDC auth flows (authorization code, client credentials) or strong motivation to learn - Understanding of web security fundamentals : CSRF, XSS, cookie security, TLS - Experience with Docker and docker-compose - Proficiency with Git and collaborative development workflows - Understanding of Nginx and web server configuration - Solid experience writing unit tests and maintaining high code quality - Good English reading skills (technical documentation) - Preferred: Understanding of microservices architecture and distributed systems trade-offs (consistency, availability, failure modes) - Experience with REST API design and documentation ( Swagger/OpenAPI ) - Hands-on experience with CI/CD pipelines - Familiarity with the Ory ecosystem (Hydra, Kratos, Keto) or similar identity management frameworks - Knowledge of PKCE , client credentials, device flow, token introspection, and refresh-token strategies - Experience with CockroachDB or other distributed SQL databases (multi-region deployments, clock skew handling) - Experience with NATS , Kafka , or RabbitMQ for event-driven / message-streaming patterns - Familiarity with Jira for project management - Understanding of Kubernetes and container orchestration - Familiarity with compliance requirements relevant to IAM: SOC 2 , ISO 27001 , GDPR data minimization, audit logging - Practical, up-to-date experience with modern AI tools (e.g. Claude, Copilot, Cursor) for code generation, review, and accelerating day-to-day engineering work

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