Senior Product Security Engineer (USA Only, 100% Remote) at Close · LumiJobs

Responsibilities

Close is a CRM built around the communication tools sales teams use every day: email, calling, SMS, workflows, reporting, and AI. Underneath that product is a broad technical surface — Python services and a large application backend, a TypeScript and React frontend, public APIs, Docker and Kubernetes, AWS infrastructure, and integrations with providers that handle sensitive customer data.
Security work happens across it all today, but the ownership is spread across Engineering, Infrastructure, and Security & Trust. We’re hiring our first dedicated Product Security Engineer to make that work systematic. You’ll report to the Backend Platform team manager within EPD (Engineering, Product, and Design), while working across the entire product and infrastructure surface. You’ll find vulnerabilities, determine which findings matter most, and drive them through remediation. Often you’ll fix the problem yourself. Other times you’ll give the owning team a clear reproduction, a practical path forward, and enough context to prioritize correctly.
You’ll analyze code, build proof-of-concepts, test running applications, tune or replace noisy tools, and automate the repetitive parts of vulnerability management. This is not a role where you forward scanner alerts and call the queue managed. Product and application security will be your responsibility. You’ll partner closely with our Infrastructure team on cloud security, access, and secrets, and with our Security & Trust Lead on GRC Engineering, compliance (SOC 2) goals, audits, and corporate security.
This role is a new one at Close. You’ll have significant room to decide where better tooling, clearer ownership, and a small amount of code can reduce the most risk.
Our backend is primarily Python, with Flask and FastAPI services and TaskTiger and Temporal handling much of our asynchronous work. We expose REST and GraphQL APIs and store data in MongoDB, PostgreSQL, Elasticsearch, and Redis.
Our frontend is a large single-page TypeScript application built primarily with React. We bundle with Vite, target modern browsers, and test with Vitest, React Testing Library, Playwright, and Chromatic. The product updates in near real time and uses technologies including WebSockets and WebRTC. Our mobile application is built with React Native.
We build and test Docker images in CI/CD and continuously deploy them to Kubernetes on AWS. Our infrastructure uses managed services including EKS, MSK, and ElastiCache, alongside services running on EC2. Terraform and Ansible automate much of the underlying infrastructure, and our containerized local development environment lets engineers run the full system on their own machines.
For this role, our stack extends beyond simply backend or frontend: browser behavior, frontend state, API authorization, asynchronous processing, data access, third-party integrations, containers, and cloud configuration can all be part of the same attack path.
We love open sourcing our code and ideas on our GitHub and on The Making of Close, our behind-the-scenes Product & Engineering blog. Check out our open source projects like SocketShark, TaskTiger, LimitLion and ciso8601.
AI is both how we build and what we ship, and that's reshaped what engineering looks like. This is a transformation we’re embracing and find deeply exciting.
An application security engineer who writes code. You can move from reading an unfamiliar code path, to reproducing an exploit, to proposing or shipping a production-quality fix. Strong Python or TypeScript experience would be especially useful; fluency across both backend and frontend systems is even better.
Skilled at finding vulnerabilities conventional scanners may miss. You use modern AI-assisted review pipelines, guided by expert judgment, to uncover subtle flaws in web apps and APIs—from authentication, authorization, and tenant isolation to injection, SSRF, unsafe data flows, and business logic. You can threat-model designs, white-box review code, and test running systems.

Senior Product Security Engineer (USA Only, 100% Remote)

Responsibilities

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