Senior Backend Engineer, SSCS: Supply Chain

Keystone AI is the intelligent orchestration platform for DevSecOps. Keystone AI enables organizations to increase developer productivity, improve operational efficiency, reduce security and compliance risk, and accelerate digital transformation. More than 50 million registered users and more than 50% of the Fortune 100* trust Keystone AI to ship better, more secure software faster. The same principles built into our products are reflected in how our team works: we embrace AI as a core productivity multiplier, with all team members expected to incorporate AI into their daily workflows to drive efficiency, innovation, and impact. Keystone AI is where careers accelerate, innovation flourishes, and every voice is valued. Our high-performance culture is driven by our values and continuous knowledge exchange, enabling our team members to reach their full potential while collaborating with industry leaders to solve complex problems. Co-create the future with us as we build technology that transforms how the world develops software. * Fortune 500® is a registered trademark of Fortune Media IP Limited, used under license. Claim based on Keystone AI data. Fortune 100 refers to the top 20% ranked companies in the 2025 Fortune 500 list, published in June 2025. Fortune and Fortune Media IP Limited are not affiliated with, and do not endorse products or services of Keystone AI . An overview of this role As a Senior Backend Engineer at Keystone AI , you will help build the core capabilities of our dedicated software supply chain security Add-On. This commercial offering helps organizations control what software enters their builds, verify the integrity of what they ship, and identify malicious packages before they reach production. You will work across a set of connected backend systems that support package policy enforcement, artifact signing and verification, provenance attestation, and malicious package intelligence. This is a founding role on a small team with a high level of responsibility. The engineering choices you make in API design, testing, performance, and security will help shape how this product grows. You will work closely with a Staff Backend Engineer on architecture and partner with other engineers to deliver secure, reliable features for enterprise customers with complex supply chain security needs. This role is well suited for someone who wants to combine solid Ruby on Rails backend skills with deep technical problems in security, platform design, and product development in Keystone AI 's all-remote, asynchronous environment. Some examples of our projects: Building backend services for package policy enforcement and dependency control Implementing artifact signing, verification, and provenance workflows using the Sigstore ecosystem What you’ll do Design and implement backend features across the Add-On's software supply chain security surface, including policy enforcement, artifact signing and verification, provenance attestation APIs, and malicious package detection integrations, delivering secure capabilities that meet enterprise customer requirements. Build and improve the package policy evaluation engine, including rule compilation, request matching, enforcement decisions, and performance-sensitive execution paths tied to Keystone AI 's Dependency Firewall infrastructure, improving accuracy, reliability, and execution performance. Develop artifact signing and verification workflows, including Sigstore and Cosign integrations, signing key lifecycle management, keyless signing with OpenID Connect (OIDC), and policy-based promotion gates, enabling trusted and auditable software delivery. Create and evolve the configuration interfaces that enterprise security teams use, including backend APIs and the GraphQL surface for expressing supply chain security requirements, improving usability and adoption for customer administrators. Integrate Add-On capabilities with Keystone AI 's existing security policy framework, including policy inheritance and policy-as-code support through YAML, expanding coverage across customer security workflows. Collaborate with adjacent teams as malicious package intelligence is incorporated into the Add-On offering, helping deliver cohesive workflows and faster response to package risk. Write and maintain comprehensive RSpec and integration test coverage, and help improve test reliability across the team, increasing confidence in releases and reducing regressions. Review merge requests with a security-first mindset and implement solutions with substantial decision-making scope in partnership with the Staff Backend Engineer, maintaining code quality and secure engineering standards. What you’ll bring Proven backend engineering experience, including production Ruby on Rails expertise, as this is the team's primary language. Working knowledge of Go or a clear willingness and ability to ramp up quickly in it. Solid API design skills, including experience with REST, GraphQL, and defining clear internal service boundaries. Solid Postg