---
title: 'Senior Full Stack Engineer (Back-End) at Sauna'
canonical: 'https://feeny.ai/job/senior-full-stack-engineer-back-end-sauna-san-francisco-xm6ndd6hmd8v'
type: 'job'
last_seen: '2026-10-14'
---

# Senior Full Stack Engineer (Back-End) at Sauna

- **Company:** Sauna
- **Location:** San Francisco, CA
- **Compensation:** $180k–$240k
- **Employment:** full-time
- **Posted:** 2026-03-09
- **Last confirmed live:** 2026-10-14
- **Apply:** https://jobs.ashbyhq.com/sauna.ai/5d64bf9c-e367-4688-a0cf-d7f7d3c4e92c

## Job description

⚠️ Please read first

- This is a full-time, in-person role based in San Francisco (Presidio) - we work from the office 5 days a week.
- You must be based in the Bay Area or willing to relocate before starting.
- We require US work authorisation, but are open to O-1 or J-1 visa sponsorship for exceptional candidates.

## About Sauna by Wordware

Every tool you use was built as an island, so you became the glue between them: a name from Gmail into the CRM, a time from the CRM into Calendly, a note from Calendly into a doc. AI showed up and mostly became an eleventh window to paste into. Sauna is a hybrid of AI and software standing on one shared brain. It holds your context and hands you real software built on top of it, so an ordinary Calendly becomes one that writes the invite itself and knows which of your busy hours bend, and for whom. Software for the path you repeat, AI for the edge that never repeats. Wordware is the team behind it, 15 people backed by Spark Capital, Felicis, and Y Combinator with a $30M seed, the largest in YC's history. We build from an office in the Presidio, fifty metres from Crissy Field beach, and we work absurdly hard because we can see and feel the outcome every day.

About the Role: You'll write and ship full-stack features end to end, from the agent runtime and backend APIs, to the web and desktop UI that users interact with every day. We're still ~20 people and shipping to our first paying users. You won't just be building features, you'll be making the decisions that determine whether this system holds at 1000x the current load. What You'll Do: You'll work directly with our CTO. Here are a few examples of the kinds of things you might work on:

- Build and operate the sandbox infrastructure where agents execute code, process isolation, resource limits, secure credential handling across thousands of concurrent sessions.
- Design the deployment and migration pipeline for a Cloudflare Workers + [Fly.io](http://Fly.io) http://Fly.io architecture, including blue-green rollouts and canary patterns.
- Instrument real-time workloads end to end: SSE streaming, task queues, and multi-model LLM provider routing.
- Ship new backend capabilities, tool integrations, scheduled task execution, memory indexing, and see them used by real people the same week.
- Reduce operational toil for a small team: structured logging, tracing, monitoring, and incident response tooling that actually works at our scale.
- Plus whatever you see that needs building.

Stack: TypeScript, Cloudflare Workers, Durable Objects, Hono, Drizzle ORM, Postgres, Zod, Vercel AI SDK, Docker, React, Vite Who You Are: Minimum:

- You have 5+ years of engineering experience building and operating backend systems in production. You've been on-call.
- You're fluent in TypeScript and comfortable working across the stack, but your instinct is to go deeper on the backend.
- You've built real-time systems: WebSockets, SSE, event streaming, or message queues in production.
- You have distributed systems intuition, you understand consistency tradeoffs and have opinions about them.
- You've shipped infrastructure to real users, not just internal tooling.

Bonus (but not required):

- You've worked with Cloudflare Workers, Durable Objects, or serverless compute at the edge.
- You've built agent systems, model routing layers, or tool-use architectures with LLMs.
- You've been a founder or early-stage engineer and care deeply about product.

Compensation & Benefits: Base salary: $180K–$240K + meaningful early-stage equity + health, dental, 401(k), considerable PTO, gym budget, lunch. x

The Process: We keep our process simple. Exceptional candidates go from first touch to offer within 2 weeks.

1. Application: Submit your resume and answer a few short questions.
2. 15-minute intro call: Quick check to align on location, motivation, and logistics. If it's a go, we move fast from here.
3. 45-minute technical interview: You'll work through a real backend problem. We're looking for fluency, depth, and how you think about systems.
4. System design interview: A deep dive into how you architect systems. We'll walk through a real Wordware problem together.
5. Final conversation: We answer your questions and scope out the work trial.
6. Work trial: Paid trial to work on a real project in person with us, usually a few days to two weeks (flexible to do what works for you). See how we work and whether this feels like the right fit on both sides.

## About Sauna

## Company Overview
- **One-liner**: Sauna is building a multiplayer AI agent that learns how you and your team work, remembers everything that matters, and acts on your behalf across thousands of connected tools.
- **Entity Type**: Private (Seed stage)
- **Headquarters**: San Francisco, CA, USA
- **Founded**: Not publicly available
- **Founders**: Not publicly available (company is described as being built by "ex-YC founders")

## Core Business
- Primary industry/industries: Artificial Intelligence, Enterprise Software, Productivity
- Target customers: B2B, teams and knowledge workers
- Mission or purpose statement: To create an AI agent that works as a teammate—running in the background, learning context across sessions, and getting work done even when users are offline.

## Products & Services
- **[Sauna AI Agent]**: A cloud-based AI agent that connects to over 3,000 tools and apps (Linear, GitHub, Notion, Gmail, Google Calendar, Jira, HubSpot, Stripe, etc.). It drafts messages, tracks what matters, files tickets, and delivers briefings. It is "multiplayer"—teammates share a Sauna's context and memory, and individual agents can communicate with each other. Available on web app, iOS, iMessage, Slack, and email.

## Market Standing
- **Valuation/Market Cap**: Not disclosed
- **Key Metric**: Total funding of $30M (largest seed round in YC history)
- **Notable Investors/Partners**: Y Combinator, Spark Capital
- **Growth Signals**: Named "Makers of the #1 Product of All Time on Product Hunt"; launched publicly on April 29, 2025; currently 18 employees; shipping to first paying users; described as building "Cursor for knowledge work"

## Competitive Advantages
- **Multiplayer AI**: Unlike single-user AI assistants, Sauna allows entire teams to share context and memory, and individual agents can communicate peer-to-peer.
- **Always-on Cloud Agent**: Runs 24/7 in the cloud, working even when the user is offline—drafting, tracking, filing, and briefing autonomously.
- **Massive Tool Integration**: Connects to over 3,000 tools and apps, with custom MCP connector support.
- **Record Seed Round**: The largest seed round in YC history signals strong investor confidence and ample runway.

## Strategic Focus
- Current priorities include scaling the agent runtime to handle 1000x current load, building out sandbox infrastructure for secure code execution, and expanding the product to serve more team workflows. The company is hiring heavily across engineering, product, and growth roles to accelerate product-market fit.

## Why Work Here
- **Culture**: Early-stage startup (18 people) with a "ship fast" ethos—one-week sprints, weekly demos, and features going from sketch to launch in days. The company uses its own product daily.
- **Work Policy**: Fully in-office, five days a week at the Presidio in San Francisco. Relocation required for non-local candidates.
- **Compensation**: Competitive base salary ($180K–$240K for Senior Full Stack Engineer), meaningful early-stage equity, health/dental, 401(k), considerable PTO, gym budget, and lunch provided.
- **Engineering Culture**: Work directly with the CTO; own infrastructure decisions that determine system reliability at scale; build real-time streaming, task queues, and multi-model LLM routing.
- **Hiring Process**: Simple and fast—exceptional candidates can go from first touch to offer within 2 weeks. Includes a paid in-person work trial (a few days to two weeks).

## Sources
1. [sauna.ai](https://www.sauna.ai/)
2. [builtin.com - Sauna Jobs](https://builtin.com/company/sauna/jobs)
3. [ainative.careers - Product Manager at Sauna](https://ainative.careers/jobs/sauna-product-manager)
4. [jobs.ashbyhq.com - Growth @ Sauna](https://jobs.ashbyhq.com/sauna.ai/56f92234-3ad1-4eaf-8f95-c53fa15af0a0)
5. [builtin.com - Senior Full Stack Engineer (Back-End)](https://builtin.com/job/senior-full-stack-engineer-back-end/9906576)

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