Senior Engineer, Backend/Infra
Agentmail Yc S25
San Francisco, CA · $250k–$400k a year · Posted March 9, 2026
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About the job
Location: San Francisco, CA
Type: Full-time, on-site
TLDR: we are seeing a surge in market demand as agents become real first-class citizens of the internet, and we are aggressively hiring in order to keep up. We're coming up with solutions in a problem space where no one in Silicon Valley knows the answer to either: how to build something agents want. If you like owning things 0 -> 1, lets chat.
AgentMail is building an API designed to give inboxes to AI agents and be the sole identity + communication provider. It isn't AI for your email, it's email for your AI.
We’re looking for a founding engineer with strong backend and infra instincts to help build the primitives agents will use to communicate, authenticate, and operate in the real world. This is a role for someone who likes systems work: APIs, distributed infrastructure, reliability, developer tooling.
Company highlights:
- World-Class Team: Founded by a team of experts in their own respects(Quant, SWE, Private Equity), the team has top-tier talent from startups and big companies alike, with backgrounds from Optiver, NVIDIA, Amazon, Modern Treasury, KKR.
- Hypergrowth: We’ve doubled our user count every 2 weeks since January, and don’t plan on slowing down any time soon. As agents will outnumber humans very soon, we see this multiple changing in the range of orders very soon.
- Competitive-edge: We are the sole identity provider for agents. Just like you have a Gmail, agent’s will need an AgentMail.
WHAT YOU’LL DO
- Lead and manage a team of 4-6 engineers
- Design APIs and abstractions that are intuitive for both humans and AI Agents
- Build high-performant, low-latency systems with the idea that agents are the end-users in mind
- Get your hands dirty by touching our core infrastructure that processes hundreds of thousands of emails per day.
- Think creatively about being the bridge between cutting edge AI capabilities with something as primitive as email(an oxymoron we know)
- Own projects end-to-end, from system design to production rollout
- Write clear, maintainable code and strong technical documentation
- Be the frontline for feedback from our customers - we’ll trust you to be our spokesperson
WHAT WE’RE LOOKING FOR
- You want to solve problems end-to-end: every engineer owns a part of the product and needs to make decisions across the frontend, infrastructure, backend, and UX.
- You have a high bar for quality: At a startup, speed is the only advantage we have over big-tech companies. But even more important is to care about your output and obsess about details.
- You are a clear thinker and communicator: We have daily standups and weekly syncs in which we expect you to communicate tradeoffs, problems, and blockers directly.
- You are highly technical: preferred you have prior experience shipping production software by real users as a software engineer at a tech company or startup. But hustlers are always appreciated.
BONUS POINTS
- Experience with cloud infrastructure, distributed systems, or developer tools
- Experience with messaging, email, auth, or protocol-heavy systems
- Experience building for AI/LLM use cases
Qualifications:
- Has 3+ years of work experience as an engineer working on infrastructure at a tech company
- Has architected software used in production by millions of users
COMPENSATION:
- $250k - $400k base salary
- 1.0% - 2.0% equity
- Breakfast, lunch, and dinner (Doordash)
- Medical, dental, and vision insurance
- Equinox membership