Full-Stack Engineer (Ruby on Rails)

Role: Full-Stack Engineer (Ruby on Rails Experience Preferred)

Experience: 2-6 years (and loves building fast while making a huge difference in the world)

Location: New York, NY

Working pattern: Two or more days per week in the office

Compensation: Top-of-market salary with significant room for growth; commensurate with experience.

Start Date: ASAP

ABOUT COSIGN

Cosign is the fastest growing proptech company in the United States revolutionizing the $4 trillion rental industry with a market-leading one-of-a-kind rent guarantee product. Our mission is to expand housing access for renters and boost occupancy for landlords. Backed by top entrepreneurs, venture capital firms, and real estate investors, Cosign is built by experienced landlords and managers for landlords and managers who deeply understand the rental market’s needs.

OUR MISSION CONTINUED

Cosign is on a mission to expand access to housing by helping landlords approve more qualified renters—without increasing risk. We partner with owners and property managers to close the qualification gap caused by conditional approvals, thin credit files, and the absence of guarantors, materially improving leasing conversion and occupancy. We’re building toward a near future where every U.S. property offers Cosign to renters who struggle to qualify—expanding housing choice while helping owners and operators convert demand into signed leases.

OUR HIRING PHILOSOPHY

At Cosign, we seek exceptional talent with relentless intellectual curiosity—individuals who:

• Challenge the status quo and drive continuous improvement
• Demand excellence from themselves and their colleagues
• Identify and solve problems others don't even recognize
• Create innovative solutions others believe impossible

We deliberately seek these rare, high-impact performers who attract similar talent. While most companies avoid hiring these exceptional individuals due to their demanding nature, we actively pursue them. When we find someone extraordinary, we move quickly to bring them onboard.

We believe average talent builds average companies. By assembling a team of exceptional performers, we're creating the talent density needed to transform the rental industry and set new standards of excellence.

THE OPPORTUNITY

As a Full-Stack Engineer at Cosign , you’ll be a core technical contributor building and scaling the product that powers our rent guarantee platform. You’ll work closely with product, operations, and leadership to deliver features that directly increase housing access and landlord occupancy across the U.S.

This is a high-ownership role ideal for an engineer who thrives in fast-moving environments, enjoys working across the full stack, and wants to help shape both the product and technical direction of a rapidly growing proptech company.

You’ll be joining early enough to have real influence on architecture, product decisions, and engineering culture.

WHAT YOU'LL DO

• Build high-impact full-stack features that directly help renters secure housing and landlords increase occupancy
• Design, implement, and scale backend systems as Cosign grows rapidly
• Collaborate with Product and Leadership on roadmap planning, technical architecture, and system design decisions
• Own features end-to-end—from backend logic and APIs to frontend implementation
• Improve reliability, performance, and developer experience across the codebase
• Contribute to technical standards, best practices, and long-term platform scalability

OUR TECH STACK

• Backend & Database: Ruby on Rails, Ruby, PostgreSQL
• Frontend: React, JavaScript, TypeScript, HTML, CSS
• Infrastructure: Render.com
• Other Tools: AppSignal, GitHub Actions, Resend, Cloudflare (R2)

WHAT WE'RE LOOKING FOR

• 2+ years of professional engineering experience with strong Ruby on Rails expertise
• Strong React / JavaScript experience (frontend is React-focused)
• Full-stack mindset—you’re comfortable working across backend, frontend, and infrastructure
• CS degree or equivalent engineering background
• Ability to thrive in a fast-paced startup environment with high ownership and minimal process
• Strong problem-solving skills and comfort working in ambiguous problem spaces

WHY JOIN COSIGN

• Work on a mission-critical housing problem and one of the biggest issues facing landlords and property managers
• Take on a foundational role with significant ownership, visibility, and influence on Cosign’s technical direction
• Top-of-market health benefits
• Laptop and full equipment setup provided
• Team offsites twice per year