Sergei Udalov Senior Backend Engineer sergei.udalov@gmail.com | linkedin.com/in/sergeiudalov | github.com/sergio-fry | Remote | European hours 12 September 2026 Re: Senior Backend Engineer, Plan: Spec-Driven Development Dear GitLab team, I'm applying for the Senior Backend Engineer (Plan: Spec-Driven Development) role. Turning a stated intent into a refined work item, a plan and verified, mergeable code is the most interesting problem in our field - and it sits where my background does: large Rails codebases and a serious interest in AI/LLM engineering. For 15+ years I've built and owned backend systems that carry real traffic - e-commerce, fintech, nation-scale infrastructure. I've taken products from zero to production, migrated systems under live load, and cut inventory synchronization from 20 minutes to 2 with ClickHouse. Most of it was cross-team, mentoring included. Technically I'm strongest in Ruby and Rails, with PostgreSQL, Kafka, ClickHouse and Kubernetes as daily tools. I treat API design, data models and observability as design constraints, and I've led monolith-to-microservices work and built shared frameworks other teams adopted. On the AI side I built an LLM voice bot with LangChain that took on about 7% of routine payment inquiries - an early lesson in measuring the quality, cost and failure modes of model-driven workflows. What draws me to GitLab is an all-remote, async-first culture and genuinely early-stage product work. I work in writing - specs and docs others can pick up - and I'm comfortable shaping scope with product and users. Python is my honest gap: I've shipped Ruby, Go and PHP, and I'd ramp up in Python without overselling the depth. I work fully remote and keep European hours, so a distributed team across Canada and Europe fits my normal working day. I'd be glad to talk about how I can help build the intent-to-code loop. Thank you for your time and consideration. What I bring - 15+ years Ruby on Rails in production at scale - PostgreSQL | Kafka | ClickHouse | Kubernetes | API design - LLM features, agentic workflows, evaluation mindset Best regards, Sergei Udalov