Full-Stack Engineer (Ruby on Rails)

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

Location: New York, NYWorking 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: ASAPABOUT COSIGNCosign 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 PHILOSOPHYAt 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 scalabilityOUR TECH STACKBackend & Database: Ruby on Rails, Ruby, PostgreSQLFrontend: React, JavaScript, TypeScript, HTML, CSSInfrastructure: Render.com Other Tools: AppSignal, GitHub Actions, Resend, Cloudflare (R2)WHAT WE'RE LOOKING FOR2+ 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 infrastructureCS 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 spacesWHY JOIN COSIGNWork 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