Senior GenAI Full-Stack Engineer - Brazil

Design and extend production-grade LLM applications and agentic workflows using

NestJS, XState v5, and the OpenAI SDK — flows include RAG, intent detection,

clarification, fulfillment, escalation, tool-use, and human-in-the-loop state machines.

Key Responsibilities

• Build and maintain the conversation-machine substrate: guard/action registries, flow validation (ajv), DB-driven flow configs, and design-time tooling in Epicenter admin.
• Build and evolve the AI systems behind Epic Support Assistant (ESA), the player-facing support chatbot, and Agent Support Assistant, the AI copilot used by customer support agents.
• Integrate with MCP servers (Model Context Protocol) for tool-use and agentic behaviors.
• Evaluate, benchmark, and tune models across providers including OpenAI, Gemini, Anthropic, and future providers; own model selection decisions balancing quality, latency, throughput, reliability, and cost.
• Troubleshoot production LLM issues including hallucinations, retrieval failures, prompt regressions, model drift, token inefficiencies, latency bottlenecks, and provider outages.
• Build resilience mechanisms: retries, fallback routing, caching, streaming, rate limiting, and provider routing.
• Instrument and tune model quality using Langfuse (tracing, evals, prompt management), evaluation datasets, A/B testing, prompt versioning, and production telemetry.
• Manage async workloads via BullMQ and caching with Redis; PostgreSQL persistence via Kysely.

Requirements

Must-Have

• Proven experience building and operating production LLM-powered systems similar in scope to chatbots, AI assistants, agent copilots, RAG systems, or LLM orchestration platforms.
• Strong TypeScript/Node.js engineering; TypeScript strict-mode fluency.
• Production AI experience: prompt engineering, RAG pipelines, agent design, tool calling, model evaluation, observability, and failure-mode analysis — you've shipped AI features, not just prototyped them.
• Fullstack depth: comfortable moving between NestJS APIs, React UIs, databases, infrastructure, and production operations; you don't artificially limit yourself to one layer.
• Ability to evaluate tradeoffs between model quality, latency, reliability, throughput, and cost.
• Ability to troubleshoot AI systems across prompts, retrieval pipelines, model configuration, infrastructure, and application code.
• State machine thinking — you naturally model complex async workflows; XState or similar experience is a strong signal.
• Solid understanding of REST API design, async patterns (queues, events), and caching strategies.
• Strong testing culture: unit, integration, and contract tests are first-class deliverables, not afterthoughts.
• Experience working in a monorepo with multiple interconnected services.

Strong Plus

• Hands-on experience with MCP (Model Context Protocol) or building tool-use agentic workflows.
• Familiarity with Langfuse or other LLM observability/evaluation platforms.
• Experience operating AI workloads at scale.
• Experience evaluating multiple foundation models and providers.
• Experience building AI copilots, assistants, or conversational products.
• Experience with semantic search and retrieval architectures.
• Experience with AI gateways such as Portkey or similar platforms.
• Experience with NestJS specifically: modules, providers, guards, interceptors, DI patterns.
• Background in customer support or player support platforms — you understand the stakes of getting AI-generated responses wrong.
• Experience shipping under low-latency constraints (chatbot response time budgets, streaming).
• Previous work in gaming or high-volume consumer products.