Senior Fullstack/Backend Engineer

Job description

ABOUT SUNBEAM sunbeam https://withsunbeam.com is building a fully autonomous SEO agent. It monitors rankings and competitors, finds content and technical SEO opportunities, writes and improves pages, and publishes to the customer's website. The agent runs 24/7. It proactively finds work to do, prioritizes tasks, and executes across tools, messaging its manager in Slack when it needs context or approval. We are not building a chatbot. We are building an employee. WHY US We ran an SEO agency https://www.withdaydream.com/ before building sunbeam. We did SEO for Clay, Replit, Hims & Hers, Rho, and others. We know the work deeply, and we are encoding that expertise into an agent that can do the job with full independence. We have raised $20M+ from First Round Capital, Basis Set Ventures, WndrCo, and SOMA Capital. We are starting with SEO, but the long-term goal is every acquisition channel. Marketing services is a $1T/year industry. If AI has automated coding, marketing is next. THE ENGINEERING CHALLENGE Fully autonomous agents are still mostly unsolved. sunbeam has to plan and prioritize work across weeks and months without a human prompt. It has to reason from messy customer context, durable memory, live search data, CMS state, analytics, and prior decisions. It has to use tools safely, know when to act, know when to ask, recover when integrations fail, and keep improving as it learns more about the company. The next years of AI will be defined by this shift from "ask → answer" to "observe → act." WHAT YOU WILL DO - Act as the technical lead for day-to-day engineering execution across the team, designing core system architecture, guiding implementation decisions, and setting standards for quality and reliability. - Build scalable, concurrent GraphQL APIs for everything from user auth/signup, to subscriptions for messaging and agent events. - Think about product security top-down, implementing it across services and access boundaries. - Build observability and evaluation workflows so we can understand agent behavior, catch regressions, and measure whether Sunbeam is getting better at the job. - Work primarily across backend systems, data pipelines, and AI-enabled services, using Python, TypeScript, and C#, deployed on Google Cloud. - Ship quickly across the stack. On a given week, you might improve our dashboard metrics, add a feature to debug Sunbeam's thought process, experiment with ideas for complex integrations, refactor our codebase, and fix an inconsistency in our message ingestion system. WHAT WE ARE LOOKING FOR - You have been building backend systems for 3+ years, with experience in production scalability, security, observability, and LLM agents, evals, tool-use systems, retrieval/memory systems, or workflow automation. - You want to understand the customer problem deeply enough to encode judgment into software. - You are comfortable working across the stack and across levels of abstraction: from "what should the agent do next?" to "why did this Postgres row end up in the wrong state?" - You are excited by early-stage ambiguity, fast iteration, and a small team where everyone touches product, engineering, design, and customer problems. - You have a consistently high bar for code quality, reliability, and technical excellence. NICE TO HAVE - Experience at a marketing, sales, or growth AI company. - Experience building from 0 to 1 and 1 to 10 at an early-stage startup. - Familiarity with C#, .NET, TypeScript, React, GraphQL, Postgres, or MCP-style tool integrations. THE TEAM Small team, San Francisco office, shipping every day. - Shravan (CTO), formerly an Engineering Lead at Flixed and a Software Engineer at Facebook, where he worked on mass-scale web scraping for Facebook Jobs and Meta Reality Labs. - Nico (Product), previously led growth at daydream and ran SEO for Anthropic, Clay, Replit, and others. - Vishruth (Founding Applied AI Engineer), previously a Data Scientist at Klaviyo specializing in NLP, with a research background from Cornell. - Daniel (Founding Applied AI Engineer), formerly a Data Engineer on Tesla's Autopilot team and previously Lead Data Engineer at Replit. - Tom (Founding Designer), who previously led product design at Blockless and now leads our frontend efforts. LOCATION This role is based in San Francisco and requires in-person collaboration five days a week. We offer paid relocation for candidates outside the Bay Area. COMPENSATION & BENEFITS $180,000–$280,000 base salary range plus equity. Medical, dental, and vision insurance. Lunch on in-office days. Wellness and learning stipends. Two retreats a year. Frequent team dinners and outings.