Senior Full Stack Engineer (Back-End)

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.iohttp://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

Artificial Intelligence (AI), Customer Relationship Management (CRM), Application Programming Interface (API), User Interface/Experience (UI/UX), Desktop PC, Memory Hardware, Incident Response, Machine Tool, Engineering, On Call, * 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.

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

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.