Senior Software Engineer - Full Stack

Cinder is the mission-critical infrastructure that keeps the world's most important digital platforms true to what they stand for. The internet has always been abused by bad actors, and AI is making it exponentially worse, driving fraud, abuse, and manipulation at a scale and speed no human team can fight alone. Cinder gives platforms one command center to fight back: to write and enforce policy, deploy AI agents against abuse in real time, investigate threats, file NCMEC reports, and prove their safety programs are working.

Our customers are some of the largest internet platforms in the world. The decisions made in our software directly determine what stays up, what comes down, and how users are treated.

We're a small, fast-moving team backed by Accel and Y Combinator. We care about being intentional, direct, and deeply focused on solving real customer problems.

You'd be building the infrastructure that some of the largest online communities in the world depend on to function. The problems aren't hypothetical: state-sponsored disinformation, CSAM reporting, coordinated abuse at scale. The software you build is used daily by the reviewers, investigators, and T&S leads making the calls that define what a platform stands for. This is an early-stage company with a mature product and real enterprise customers. You'll have outsized influence on architecture, product direction, and engineering culture.

This isn't a generic full-stack role. Here's what's actually on the roadmap right now and what you'd be contributing to:

• AI agents that review content against customer policies, callable from within our durable workflow engine. We're moving from hardcoded LLM prompts to a configurable agent spec that customers can edit and deploy themselves.

• A workflow engine built on Restate for durable execution. Engineers build new nodes that customers wire together to automate moderation pipelines, NCMEC reporting, enforcement actions, and more.

• Review queue tooling: the core UI where moderators and investigators spend their day. You'd work on features like QA decision overrides, attribute-level labeling, forms, and skills-based routing.

• Analytics and metrics dashboards that help T&S leads understand how their programs are performing, built with a React frontend backed by a Django/GraphQL API.

• Two-way user communications: building integrations (Salesforce, Zendesk) so moderators can contact users and see conversation history without leaving Cinder.

• Reliability at scale. Our customers process high volumes of content through review queues, workflows, and AI agents. You'd help define SLIs, improve pipeline throughput, and own oncall for systems where downtime means moderation stops.

• 5+ years building production software, with experience across the stack: Django or similar backend frameworks, React or similar on the frontend, relational databases, and message/event systems.

• You've identified a customer problem yourself, not just been handed a ticket, and built an end-to-end solution for it. We don't operate with a traditional PM-led design approach at Cinder. Engineers participate in customer demos, hear feedback firsthand, and shape what gets built next.

• Experience with high-throughput, data-intensive systems. Our platform ingests large volumes of entity data, events, and media from customer platforms. You should be comfortable reasoning about pipeline throughput, latency, and the tradeoffs that come with scale.

• You have a real point of view on how AI tooling has changed the way you write code. We use it extensively and expect engineers to be fluent and opinionated, not just familiar.

• End-to-end ownership. Even as AI code gen changes how frontend code gets written, you need to understand how the backend is designed to build something usable from start to finish. You'd own features from data model through API through UI.

• Clear written communication. We're a distributed team with a concentration in NYC, and we work closely with customer-facing teams. You need to write clearly in PRs, Slack, and customer-facing documentation.

• Experience in Trust & Safety or abuse prevention. Understanding how attackers exploit platforms gives you a head start.

• Experience at a startup or early-stage company where you wore multiple hats and shipped fast with limited resources.

• Familiarity with workflow/automation systems, policy engines, or case management tools.

• Experience working directly with enterprise customers or in a customer-facing engineering role.

We're based in NYC and would relocate the right person for this role. We believe in working together in person and hold at least two all-company events per year. We offer health, vision & dental benefits, a 401(k) plan with employer matching, fully paid commuter benefits, and a fully stocked office with paid lunch and dinner.