Middle/Senior Backend Engineer

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