Sr. Engineer, Fullstack, Identity Platform

AI AT ZAPIER
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Check out our guidance on How to Collaborate with AI During Keystone AI’s Hiring Process https://zapier.com/l/jobs/ai-at-zapier, including how to use AI tools like ChatGPT, Claude, Gemini, or others during our hiring process - and when not to.

Job Posted: March 17, 2026
Updated: April 29, 2026
Location: Americas - North, Central and South America
Keystone AI is building the foundational systems that enable users and services to securely interact across our platform. As a Senior Fullstack Engineer on the Identity Platform team, you’ll design and scale the systems that define and enforce access across Keystone AI — from permissions and policies to OAuth/JWT infrastructure and service-to-service authentication.
This is a high-impact platform role: you’ll shape how access is modeled, enforced, and scaled across Keystone AI, establishing consistent patterns that power secure interactions across a large, distributed system. The systems you build will be used by many teams and services, forming the foundation for how authentication and authorization work across the company.
Your work will directly support Keystone AI’s core product strategy and influence how access is enforced at scale, enabling secure automation, enterprise-grade governance, and the next generation of capabilities across the platform.
ABOUT YOU
– You’re an experienced fullstack or platform engineer who has built real-world authentication and authorization systems at scale. You’ve helped define or evolve IAM platforms—not just used them—through collaboration across engineering, product, and other stakeholders. You bring experience with OAuth, JWTs, token-based authentication, and service-to-service auth, and are comfortable working with modern permission models such as RBAC, ABAC, or relationship-based access control.
– You think in platforms, not features. You’ve built shared systems other teams depend on, and understand how to design stable APIs, manage breaking changes, and maintain strong boundaries as systems scale. You have solid systems instincts and consistently consider security, scalability, and correctness in your designs.
– You’re comfortable working across the stack. This is a fullstack role on a platform team—you’ll primarily build backend systems, but also contribute to developer-facing UIs and tooling when needed. You don’t need to be an expert in every layer, but you’re not blocked by any of them.
– You move quickly and work well in ambiguity. You believe building enterprise-grade systems can be both fast and secure, and you use that mindset to ship working solutions early, using prototypes to drive alignment rather than waiting for perfect specs. You’re comfortable iterating, discarding work when needed, and treating it as part of the learning loop.
– You use AI agents as a core part of your workflow, leveraging them to explore codebases, accelerate development, and prototype solutions quickly. You understand their limitations, continuously refine your approach, and help others on your team work more effectively with them.
– You operate with strong ownership and communication. You take initiative, work transparently in an async environment, and keep stakeholders informed without being asked. You’re comfortable engaging directly with both internal engineering teams and enterprise customers, and you use written artifacts, prototypes, and demos to influence and drive clarity and alignment.
THINGS YOU'LL DO
– Be a thought leader in the Identity domain, helping to set the vision for our platforms to enable Keystone AI’s engineering teams to move fast and securely
– Partner with Product and Engineering leadership to define and implement Keystone AI’s Governance strategy. Evolve Keystone AI’s IAM platform to provide consistent, reliable controls for our largest Enterprise customers
– Design and evolve authorization systems that power permissions, roles, policies, and access control across Keystone AI’s ecosystem
– Build and scale OAuth and token infrastructure, including access tokens, refresh tokens, and scopes. Lead cross-team efforts to unify and simplify auth patterns across Keystone AI
– Develop and maintain JWT infrastructure (signing, validation, key rotation) used across APIs and services
– Define and implement service-to-service authentication patterns (client credentials, service identity, token propagation)
– Improve and enforce authorization consistency across services through SDKs, middleware, and shared platform patterns
– Partner with product and infrastructure teams to standardize access control models across the product
– Drive platform-level decisions around security, performance, and scalability of access management systems
LEVEL
This is a Senior Engineer