Senior Backend Engineer II, Authentication & Authorization

Authentication and authorization underpin nearly every interaction on Vinted. They determine how members, employees, and services prove who they are, and what they are allowed to do.

Today, these responsibilities span our core platform, dedicated identity services, gateways, service-mesh infrastructure, and workforce systems. We are evolving this landscape towards a shared identity model and an authorization platform that is secure, reliable, observable, and straightforward for engineering teams to adopt.

We’re looking for a Senior Backend Engineer II to join the Authentication and Authorization team. You’ll work across two connected areas:

• Evolving authentication towards a consistent, federated identity model for members, employees, and systems
• Building shared authorization capabilities that replace fragmented, service-specific solutions with common concepts, APIs, tooling, and decision observability

This is neither a purely greenfield role nor a legacy-maintenance role. You’ll help extract existing functionality safely, improve production services, and build new platform capabilities.

We’re looking for an experienced engineer, but not necessarily someone who already knows every part of identity and access management. What matters is strong engineering judgement, curiosity, and the ability to learn unfamiliar technologies and domains. You should be comfortable going deep into a technical problem, then zooming out to understand how the solution affects users, services, infrastructure, security, and other engineering teams.

• Design, build, and operate backend services supporting authentication, identity propagation, token exchange, authorization decisions, and policy management
• Help extract authentication functionality from existing systems while preserving feature parity, controlling rollout risk, and retiring legacy paths safely
• Contribute to stable identity and authorization contracts that allow services to evolve without depending on individual identity providers, token formats, or API implementations
• Build shared authorization capabilities, including a capability registry, policy APIs, decision logs, and tools for understanding who or what can access a resource
• Improve supported integration paths - such as SDKs, libraries, conformance tests, documentation, and migration tooling - that make secure adoption easier for other teams
• Work with Registration, Platform, Security, and product-domain engineers to define ownership boundaries, integration contracts, and safe migration plans
• Keep security-critical systems reliable and observable by contributing to SLOs, latency expectations, failure behaviour, monitoring, and operational response
• Take ownership of complex areas of work from design through implementation, rollout, and production operation
• Contribute to technical proposals and architectural decisions, helping the team understand the available trade-offs
• Support other engineers through thoughtful code reviews, pairing, documentation, and knowledge sharing
• Write, review, test, deploy, monitor, and troubleshoot production code

You’re an experienced backend engineer who can take responsibility for difficult or unfamiliar problems. You don’t need to arrive with every answer. You’re comfortable saying, “I don’t know yet,” then learning enough to make a thoughtful decision and move the work forward.You can work across a wide technical surface without losing sight of the underlying problem. You know when to investigate deeply, when to involve someone else, and when a pragmatic solution is better than an elaborate one.

We’d expect that:

• You have a strong track record of building and operating distributed backend systems in production
• You can take ownership of complex backend work, including design, delivery, rollout, and operational follow-through
• You know at least one programming language deeply and can transfer your engineering knowledge to unfamiliar languages and ecosystems
• You’re comfortable reasoning about APIs, data models, consistency, caching, concurrency, reliability, and security boundaries
• You write clean, maintainable, well-tested code and contribute constructively to engineering standards
• You care about observability and understand that authentication and authorization systems must be explainable when something goes wrong
• You can balance security, reliability, developer experience, delivery speed, and long-term maintainability
• You communicate technical decisions clearly, including their risks and assumptions
• You collaborate effectively across team boundaries and help move shared work forward
• You share knowledge and make technical context easier for other engineers to access
• You’re curious, adaptable, and motivated by problems that require you to learn rather than simply repeat what you already know
• You have excellent written and spoken English

It’s a plus if you have:

• Experience or familiarity with authentication and authorization concepts
• Knowledge of OAuth 2.0, OpenID Connect, token exchange, identity federation, workload identities
• Understanding of RBAC, ABAC, policy-as-code, OPA/Rego
• Experience with service mesh technologies such as Envoy or Istio
• Familiarity with Go, Ruby, infrastructure as code, and Git-based delivery workflows
• Willingness to learn new technologies and apply them based on the problem at hand

• The opportunity to benefit from our share options programme
• 25 working days of holiday
• Access to all the tools & tech needed for work
• Home office support: we provide IT workstation equipment and a personal budget of up to €540 for home workplace furniture
• Private health insurance
• Mental and emotional health support through the Mindletic app
• Frequent team-building events
• A personal monthly budget for shopping on Vinted
• The opportunity to spend up to 90 days per year - 21 of which can be spent working outside of the EU - on workation
• A dog-friendly office
• In Vilnius office: Gym & in-house meals at friendly prices
• In Kaunas office: a monthly lunch allowance, and a once-a-week provided in-house lunch and breakfast

Individual Learning Budget

We invest in your professional growth! As part of our commitment to continuous learning, we offer an annual learning budget to support your personal and career development through courses, certifications, workshops and more.

Hybrid Work 

We’ve adopted a hybrid workplace model where 2 days in the office are recommended but not enforced. It’s up to you and your team to decide on the exact days you’ll spend working together in person.

Equal Opportunity

The Vinted Group is committed to building an inclusive workplace where people from all walks of life feel a sense of belonging. We welcome applications from people of all backgrounds, identities and life experiences. At Vinted, all applicants are treated fairly without regard to their race, age, religion or belief, sex, national origin, citizenship, gender identity, sexual orientation, disability, or any other protected characteristic.