Senior Backend Engineer (Nest.js)

Our client is a web platform that helps freelancers find remote jobs more effectively with AI. We’re looking for a Senior Backend Engineer to design the backend systems powering authentication, onboarding funnels, subscription logic, data processing, and AI-driven features. What You’ll Do: - Architect and scale core SaaS services, including authentication (RBAC), activation funnels, and subscription/payment lifecycles (webhooks, idempotency). - Design and manage complex, highly relational data models powering our core matching engine, including robust data processing and transformation pipelines. - Design and orchestrate asynchronous AI pipelines and LLM integrations to process complex unstructured data (CV parsing, job matching) into structured formats without blocking the user experience. - Develop high-performance, event-driven backend systems using NestJS, PostgreSQL, Redis, and NATS. - Design the APIs and logic powering our CV Builder and structured content systems. - Ensure system reliability through proactive performance tuning, caching strategies, observability, and robust failure recovery. - Own the backend architecture end-to-end, collaborating closely with Frontend and Product teams to deliver business impact. - 5+ years of commercial backend/full-stack experience with the ability to own architecture end-to-end. - Strong production expertise in NestJS, PostgreSQL (complex schema design, indexing, migrations), and Redis (caching, rate limiting). - Proven experience building scalable data processing workflows and managing evolving, heavily relational data models in production. - Proven experience building asynchronous AI pipelines and integrating LLM APIs (handling rate limits, background workers, forced JSON outputs, and fallback strategies). - Hands-on experience with NATS or other event-driven messaging systems. - Deep understanding of distributed systems (idempotency, retries, race conditions, eventual consistency). - Experience designing subscription-based SaaS systems and secure payment integrations. - Solid DevOps and security mindset: Docker, Kubernetes, Helm, auth flows, and strict PII data protection. - Market-level compensation - Office/hybrid in Warsaw or fully remote from nearby time zones (CET ±2). - 20 paid working days of vacation per year + sick leave. Dear Candidates, due to a high volume of applications, only selected candidates will be contacted for interviews. We appreciate your understanding. Thank you for considering a career with us. - Work type - Full-time - Location - Remote