Senior Product Engineer (Backend)

CareerOS is a B2B2C career platform serving 100+ top MBA programs worldwide - including Oxford, INSEAD, London Business School, Georgetown, and Notre Dame - along with 30+ employers. We help 500K+ users land jobs they love, and we're growing with real revenue (not just runway).

We're a small, high-output team of 5 engineers based in Barcelona, scaling to 10+. We work in small squads, each owning their area of the product end-to-end. We ship fast, own our decisions, and push each other to do great work.

We're looking for a Senior Product Engineer - someone who builds full features from database to UI, with strength in backend systems.

You'll work directly with the CTO and CPO, not through layers of management. You'll be in the room when decisions get made and have real input on what we build and how.

We call this a "Product Engineer" role because you won't just implement tickets. You'll own features end-to-end, make product calls, and ship things that matter to real users.

Tech stack: Node.js (primary for new code), some legacy Go (~20%), React/TypeScript on frontend. Infrastructure on GCP with Terraform.

Typical split: ~60% backend/infra, ~40% frontend - varies by project.

• Ship full features, end-to-end - From schema design to API to UI. You'll own the whole vertical, not just one layer.

• Build and maintain infrastructure - GCP, Terraform, CI/CD pipelines. You'll keep the systems running and improve them over time.

• Optimize databases - Write complex queries, tune performance, design schemas that scale.

• Make product decisions - See a better way to solve a user problem? Propose it and build it. We trust engineers to make smart calls on technical and product decisions.

• Build with AI tools - We use Claude Code, Cursor, and other AI tools daily. You should be comfortable (or excited) to work this way.

• Own your code in production - Continuous deployment means what you merge today is live today. You'll debug, monitor, and improve what you build.

Must-haves:

• 5+ years building production systems, with strong backend experience (Node.js or Go)

• Solid SQL skills - complex queries, performance tuning, schema design

• Infrastructure experience - GCP or AWS, Terraform, CI/CD pipelines

• Comfortable across the stack - backend-focused but can ship real frontend features in React/TypeScript, not just "fix a button"

• Strong product intuition - you've shipped features where you made architectural and product calls

• Excellent communication - clear writing, respectful pushback, documentation others actually read

• Comfortable with ambiguity - you ask the right questions, make reasonable assumptions, and move forward

• Fluent English - we're distributed; clear communication is essential

Strong signals:

• You've worked at an early-stage startup before (and liked it)

• Experience with auth systems - OAuth, SAML, SSO, Auth0

• Side projects or open source that show you build things because you're curious

• You've used AI coding tools and have opinions about them

• You care about craft - clean code, good abstractions, reliable systems

Let's be honest about fit:

• ❌ Not a chill 9-to-5 - Startup means more ownership, higher stakes, and hard pushes around launches. We respect personal time and recover after sprints, but when we ship, we ship hard.

• ❌ Not highly structured - If you need detailed specs and clear roadmaps to function, this isn't the place.

• ❌ Not backend-only - You'll spend real time in React. If you want pure backend/infra, this isn't the role.

• ❌ Not frontend-heavy - If you want to go deep on UI/UX, we have a Frontend Product Engineer role.

You'll join as one of 5 engineers, growing to 10+. As we scale, there's a clear path to tech lead or staff engineer for the right person. You'll help shape engineering culture, not just inherit it.

• Competitive salary + stock options - we'll discuss based on experience and location

• Remote-friendly - Barcelona hybrid optional, remote within CET ±2 hours

• Small team, visible impact - 500K+ users, real revenue, your work matters

• Work directly with CTO and CPO - fast decisions, no layers, real influence

• AI-native team - we are using Claude Code and Cursor in our day-to-day and open to trying new

Don't check every box but think you'd be great? Apply anyway. We care more about trajectory and taste than credentials.