Founding Engineer – Backend & Agent Infrastructure

CGS; San Francisco (CA); On-site; USD 180,000 - 280,000; Full time

Job summary

CGS, a seed-stage AI company based in San Francisco, is hiring its third engineer to own the core backend infrastructure and scale coding-agent sessions. You will design agent sandboxes, AI gateways, and orchestration in a hands-on role that shapes the architecture and product direction.

Expect to work on production systems from scratch with high autonomy, collaborating closely with founders. Five days on-site, 9-9-6 schedule, eligibility limited to US citizens or Green Card holders.

Qualifications

• 3+ years hands-on software engineering experience; 5+ years preferred.
• Recent experience as an IC at a fast-growing seed-stage or Series A startup.
• Proven experience designing and building production backend systems from scratch.
• Strong understanding of distributed systems, infrastructure and performance optimisation.
• Experience with TypeScript or Python, PostgreSQL, AWS and containers.
• Able to explain and defend architectural decisions, including why one approach was chosen.
• Genuine interest in AI coding agents and developer tooling.
• Comfortable working fully on-site in San Francisco, five days per week, on a 9-9-6 schedule.
• Must be a US citizen or Green Card holder. No sponsorship available.

Responsibilities

• Design and build core backend systems and infrastructure from the ground up.
• Own agent sandboxes, AI gateways and orchestration for large-scale coding-agent sessions.
• Solve real-world challenges involving system performance, reliability and scalability.
• Make independent technical decisions and take responsibility for the architecture.
• Ship customer-facing improvements quickly, incorporating feedback within days rather than weeks.
• Work closely with the founders and contribute to technical direction and product decisions.

Skills

Backend engineering

Distributed systems

TypeScript

Python

PostgreSQL

AWS

Containers

Tools

ClickHouse

Docker

Kubernetes

Job description

Location: San Francisco, CA – fully on-site, five days per week

Working hours: 9-9-6

Equity: 0.5–1%

Experience: 3+ years (5+ preferred)

Work authorization: US citizens and Green Card holders only. No visa sponsorship.

The Company

A seed-stage AI company based in San Francisco that runs real coding sessions through popular AI coding agents. Its platform helps developer-tool companies understand whether AI agents select their products, how effectively they use them, and where they encounter friction or switch to competitors.

The company already works with well-known developer-tool businesses and is growing quickly.

The Opportunity

As the company's third engineer, you will take ownership of its core backend infrastructure, with the opportunity to lead this area within your first two to three months. You will build the systems that power coding-agent sessions at scale, including agent sandboxes, AI gateways and orchestration infrastructure.

This is a highly hands‑on founding engineering role for someone who enjoys building production systems from scratch, solving complex infrastructure challenges and shipping directly to customers.

Key Responsibilities

• Design and build core backend systems and infrastructure from the ground up.
• Own agent sandboxes, AI gateways and orchestration for large‑scale coding‑agent sessions.
• Solve real‑world challenges involving system performance, reliability and scalability.
• Make independent technical decisions and take responsibility for the architecture.
• Ship customer‑facing improvements quickly, incorporating feedback within days rather than weeks.
• Work closely with the founders and contribute to technical direction and product decisions.

Requirements

• At least 3 years of hands‑on software engineering experience; 5+ years preferred.
• Recent experience as an individual contributor at a fast‑growing seed‑stage or Series A startup.
• Proven experience designing and building production backend systems from scratch.
• Strong understanding of distributed systems, infrastructure and performance optimisation.
• Experience with technologies such as TypeScript or Python, PostgreSQL, ClickHouse, AWS and containers.
• Able to explain and defend architectural decisions, including why one technical approach was chosen over another.
• Genuine interest in AI coding agents and developer tooling.
• Comfortable working fully on‑site in San Francisco, five days per week, on a 9-9-6 schedule.
• Must be a US citizen or Green Card holder. No sponsorship available.

Particularly Relevant Experience

Experience with agent infrastructure, agent sandboxes, AI gateways or orchestration is highly relevant.

Engineers who have previously been founding engineers, built infrastructure at fast‑growing AI or developer‑tool startups, or actively contribute to the agent ecosystem through open source, hackathons or side projects will stand out.

What Makes This Opportunity Interesting?

• Join as the third engineer and take ownership of critical backend infrastructure.
• Work on a product already used by recognised developer‑tool companies.
• Build systems at the intersection of AI agents and developer tooling.
• Work directly with experienced founders who have collaborated for over ten years.
• Have significant autonomy over technical decisions and the opportunity to ship improvements within days.

Interview Process

• Initial screening conversation.
• 60‑minute technical interview, including:
• Short introduction.
• Walkthrough of a production system you built, covering its purpose, architecture and key technical decisions.
• A short system‑design exercise based on a real early‑stage company challenge.