Member of Technical Staff - Sailboxes

Theory Ventures; San Francisco, Northern (CA, KY); On-site; USD 150,000 - 230,000; Full time

Job summary

Sail is hiring a software engineer in San Francisco to help build Sailboxes, our cost-efficient CPU sandbox for long-horizon agents. You’ll work across the stack, from low-level networking to large-scale systems that improve efficiency and latency.

You will focus on performance, scalability, and reliability in a rapidly growing product line, collaborating with a small, ambitious team in a hands-on environment.

Qualifications

• Strong background in distributed systems, concurrency, networking, and databases.
• Experience with large-scale production distributed systems is preferred.
• Cloud infrastructure and container orchestration experience (multi-cloud a bonus).

Responsibilities

• Dig into our FirecrackerVM fork to maximize performance of the platform.
• Model usage patterns and implement scheduling for fleet utilization and autoscaling.
• Design highly available distributed systems handling millions of ops/sec.
• Build monitoring tooling to improve operator and user experience.

Skills

Distributed systems

Cloud infrastructure

Product-focused platform work

FirecrackerVM experience

Performance engineering

Tools

Kubernetes

Docker

GCP

AWS

Azure

Job description

Sail builds the world's most efficient software for inference (processing LLM tokens) and agent hosting (cloud VMs). Together, our technologies allow our customers to deploy AI agents at large scale to do the most challenging work.

In this role, you'll focus on Sailboxes, our cost-efficient CPU sandbox for long-horizon agents. You’ll be one of the first engineers on a rapidly growing product-line and write code at every part of the agent runtime, from low-level performance work on our custom networking stack to building large scale systems that maximize our efficiency.

What you’ll do

• Dig into the guts of our custom FirecrackerVM fork to extract every ounce of performance possible from our platform.

• Model historic usage patterns and implement scheduling algorithms that maximize our fleet utilization and autoscale intelligently while minimizing latency.

• Design and implement highly-available distributed systems to handle millions of operations per second.

• Build deep monitoring tooling and features that make Sailboxes the most delightful experience for both humans and agents alike.

• Own future product directions for Sailboxes (Windows/Mac sandboxes, high-efficiency storage, etc.).

What we’re looking for

• Strong distributed systems fundamentals (concurrency, networking, databases, performance engineering). Ideally experience building and maintaining software for large-scale production distributed systems.

• Experience with cloud infrastructure (GCP, AWS, Azure), container orchestration, and/or multi-cloud networking.

• You take a product-focused approach to platform work and care deeply about building solutions that are robust, scalable, and ergonomic for users.

• Bonus: experience with FirecrackerVMs.

Interview process

1. Meet the CTO, who will ask about your experience and share as much detail about Sail as you want to hear.

2. A technical interview with one of our Sailbox engineers. This will also be an opportunity to ask any questions about the Sailbox product and team.

3. Come in to Sail's SF office for an interview day. Meet the whole team, then you'll have 3-4 hours to design and implement a solution to a problem that closely simulates the work we do daily. AI assistance is highly encouraged, and we'll provide a laptop with all the best tools set up. Finish with a short presentation describing your process, learnings, and results.

4. Offer. Once the team decides we want to work with you, we make a strong offer quickly and will be quite persistent over email/text/calls :)

Life at Sail

We work out of a beautiful, sunny office in downtown San Francisco. All meals are on us (and actually great; SF is a food paradise and it would be a shame to eat only bowl slop). Everyone gets a Studio Display at their desk. We are serious about investing in anything that saves us time or energy. There are six different ways to make coffee or tea in the office. A friendly (hypoallergenic) black cat named Coco visits occasionally.