What are the responsibilities and job description for the Senior Software Engineer (Backend) position at Harnham?
Senior Software Engineer (Backend)
Location: Los Angeles OR San Francisco
Salary: $180-220k base Equity
We're looking for a Senior ackend Engineer to help build and scale the infrastructure powering one of the most technically ambitious AI platforms in the consumer space.
This is a role at a $1B AI company on the cusp of a Series D, scaling from tens of thousands of users to 50 million in Q3. Small team, real ownership, genuinely hard problems.
The Role
Roughly 50/50 between two things.
Half is well-crafted foundational backend — APIs, authentication, microservices, the building blocks that keep the platform running reliably at scale.
The other half is high-compute infrastructure — orchestrating complex ML pipelines, managing GPU clusters, moving large model weights between systems, and keeping latency tight as the platform scales rapidly.
You'll work closely with the Lead Software Engineer and have real design ownership from day one.
What We're Looking For
Must have:
- 5 years of substantive backend engineering experience — this means production systems and real APIs, not ML scripts or frontend TypeScript
- Strong proficiency in Go, Python, or TypeScript applied to backend work — we're flexible on language but you need to be genuinely strong in at least one
- Solid understanding of core networking fundamentals — how HTTP works, how browsers communicate, what happens under the hood
- Concurrency experience — thread safety, resource management, and the ability to reason about and scale concurrent workloads
- Familiarity with modern web serving frameworks and service architecture
- Some exposure to orchestrating compute or server infrastructure — Kubernetes, ECS, or similar. Doesn't need to be deep, but needs to exist
- Strong CS fundamentals — we care less about where you've worked and more about your ability to apply core principles to novel problems
Nice to have:
- Experience with GPU cluster scaling or ML inference infrastructure
- Familiarity with heavy-compute pipeline orchestration
- Background at a well-known or high-growth tech company
What we're not looking for:
- Engineers whose entire career has been in Java with limited exposure to modern stacks
- Backend experience narrowly scoped to ML pipelines only, or TypeScript used exclusively for frontend React work
- Anyone who struggles to explain their design reasoning or spot gaps in their own solutions — the design interview is where most candidates fall short, and we coach our candidates on this ahead of time
The Stack
- Go · Python · TypeScript · Kubernetes · ECS · Terraform · REST · gRPC · Datadog
Why Join
- Pre-IPO unicorn, Series D imminent, clear path to massive consumer scale
- Novel problems at the intersection of AI and high-throughput compute infrastructure
Salary : $180,000 - $220,000