Sixtyfour helps teams understand the people, companies, and entities they interact with. With a primary focus on Compliance (AML/KYB), Trust & Safety, Cybersecurity, and Investigations. Our platform combines agents, LLMs, and large-scale data infrastructure to surface data other platforms can't.
The Role
We're looking for a Senior Software Engineer to join our core Engineering team and help build the infrastructure Sixtyfour runs on. This is a hands-on, high-ownership role spanning backend systems, API design, billing, and infra scaling. This is the kind of work that shapes not just what we ship, but how we build for years to come. You won't have direct reports, but you'll operate as a technical leader from day one: setting the standards, shaping architecture decisions, and mentoring engineers as the team grows around you.
If you're the kind of engineer who gets excited about API design, scaling infrastructure, and payments/billing systems, let’s talk.
What You'll Do
Own and evolve core backend infrastructure as we scale usage and traffic
Design and build robust, well-architected APIs that power our core product and developer platform
Build and maintain billing and payments infrastructure (Stripe)
Build and productionize agent workflows and LLM-powered systems
Drive technical decisions around scaling — performance, reliability, data pipelines, and search
Operate like an SRE when needed.
Work hands-on in the codebase daily while mentoring other engineers and helping raise the technical bar across the team
Partner directly with leadership on technical strategy and roadmap as an early, influential member of the team
What We're Looking For
3–7 years of professional software engineering experience
Experience as a team lead or tech lead — comfortable providing technical direction and mentorship without needing direct reports to do so
Strong API design and backend development experience
Experience with observability
Experience with backend infrastructure and scaling systems in production
Experience building or maintaining billing/payments systems (Stripe or similar)
Proficiency in Python and JavaScript
Experience with Kubernetes
Experience with Apache Spark
Experience with AWS: Glue, EC2, Data Pepper & CloudWatch
Experience with: Temporal
Experience with OpenRouter
Experience with LLMs, scaling infrastructure, and search
Comfortable in a fast-paced, early-stage environment with high ownership and ambiguity
Willing to be based in or relocate to the San Francisco Bay Area.
Nice to Have
Experience building developer-facing products or platforms (APIs, SDKs, dev tools)
Experience with Next.js and Vercel
Prior startup experience, ideally at a similarly early stage
Experience working in an AI company
Experience developing agents
Benefits
Unlimited PTO
Lunch on us in the office
Monthly gym membership reimbursement
Monthly AI tools/productivity reimbursement
401k with company match
Health / Dental / Vision
Flexible working hours
About Sixtyfour
Intelligence Infrastructure on People and Entities
