Founding Product Engineer

Cardinal is the AI platform for precision outbound. We run outbound for 40+ YC companies, including Mintlify, Greptile, and Luminai.

"Spray and pray" outbound is dead. The best sales teams operate with extreme precision — finding things in common with customers, monitoring their content, mapping inbound signals, and tracking website visitors. But doing this well means stringing together 10+ tools and hiring a GTM engineer. Cardinal replaces all of that.

Our AI agents find hyper-targeted leads, continuously monitor what prospects are posting and engaging with on social media, generate personalized snippets based on shared context, and orchestrate end-to-end outbound workflows across email and LinkedIn. Cardinal also captures inbound from website visitors, product signups, ad impressions, and social engagement — qualifying and routing them into sequences automatically.

Cardinal is founded by Devi and Jianna, 2x YC founders (S23, W26) and Harvard/MIT CS alums. Their last company, Leafpress, was an energy software company where they closed customers like Lindt and Honeywell from cold outbound.

About Cardinal

Cardinal (trycardinal.ai) is the AI-native outbound sales platform replacing the SDR-and-GTM-engineer stack that companies cobble together today with Apollo, Outreach, Clay, and a few engineers gluing them all together.

We're a YC W26 company. In our first few months we've grown to $80K+ MRR, with 50+ YC companies and a growing roster of post-Series-A startups running their outbound on us. We've raised over $5M from Audacious, Burst Capital, and YC, and we're targeting $10M ARR by mid-2026.

We're a small, dense, design-obsessed team. The bar for engineering taste, product instinct, and aesthetic quality is very high — if you've ever opened Linear or Attio and thought "why doesn't every B2B tool feel like this," that's the bar.

As a Product Engineer at Cardinal, you'll work on the surfaces our customers — founders, GTM leaders, sales engineers — live in every day. That includes our sequence and enrollment system (per-lead customization, multi-sender, conditional branching), the agent layer (the embedded AI agents that draft, research, and enroll on behalf of the user), and the eval and observability tooling that lets customers trust an AI to run their pipeline.

Cardinal is a system of action sitting on top of every GTM data source — CRMs, enrichment APIs, LinkedIn, intent signals, website visitor data. Our job is to make all of that feel like one beautifully designed product, not a plumbing project. You'll work directly with the founders, ship to production every week, and have an outsized influence on what the product becomes.

Philosophy: You're your own worst critic. You don't ship at 90%. You don't just file the bug — you fix it. You move fast without confusing fast for sloppy.

Product intuition: You can tell the difference between a UI that feels good and one that doesn't, and you can articulate why. You think from first principles about user workflows, not feature checklists.

GTM context: You've worked at a sales-adjacent company — an outbound tool, a CRM, a sales intelligence platform, a revenue-tech startup — or you've been the technical person at a startup who actually built and ran the outbound motion yourself. You don't need to be a sales expert, but you should immediately understand why a "step 3 reply detection" bug or a "lead enrichment timeout" matters to a customer. If words like sequence, enrollment, ICP, intent signal, deliverability, and sender rotation don't make you glaze over, we want to talk.

• Have founded a company, been an early engineer at a YC-stage startup, or shipped a product 0→1
• Have built or worked at a GTM/sales/CRM/enrichment tool — Apollo, Outreach, Clay, Attio, HubSpot, Salesforce, Gong, Common Room, or anything in that orbit
• Are a power user of GTM tools yourself — you've actually run outbound, written sequences, and fought with deliverability
• Have worked on real-time collaborative interfaces, agent UIs, or eval/observability tooling
• Care about design at the level of Linear, Attio, Raycast, or Vercel — and have shipped UIs at that quality bar

This is an in-person role at our SF office. We're early stage, which means working hard and moving quickly. Apply if that excites you.

Cardinal's stack is built for speed and scale:

• Frontend: Next.js + React + TypeScript + Tailwind CSS
• Backend: Multiple FastAPI microservices handling search, enrichment, sequencing, inbox, and webhooks
• Database: Supabase (PostgreSQL) + Redis for caching and job queues
• AI: LLM-powered agents for lead discovery, content monitoring, snippet generation, and intelligent sequence personalization

Hard problems we're solving: building AI agents that understand sales context, real-time content monitoring and signal detection across social platforms, multi-channel sequence orchestration across dozens of email domains, and enrichment pipelines that operate at scale.