Part 2 Tech Lab Full-Stack Product Engineer Own a product end to end — the users, the roadmap, the build and the release — with nobody standing between you and the people who use it. Barcelona Open 5 seats What you own 01 The users, in person 02 What gets built next, and why 03 The build, front to back 04 Whether it gets used One method, many products Mainloop is anengineering company in Barcelona. What we build is the software that automates professional-services work — across roughly fifteen countries, for businesses that are drowning in process. The other half — this half — takes what is proven and owns it for years. This is the seat where the product and the engineering are the same job. Not a slice of it, and not the tickets someone else wrote about it. You decide what it should do next, you build it, you ship it, and you find out whether it worked. You talk to the people who use it. There is no one above you writing the roadmap for your product and no one below you writing the stories. You build it, front to back. The interface, the logic underneath, the data it keeps. You decide whether a feature makes sense on the screen and whether it holds up behind it, which is exactly the judgement that gets lost when those two calls belong to different people. You ship it and you measure it. A feature is not done when it merges; it is done when people use it and the number moves. You own that number — time saved, errors avoided, uptake — and you report it whether it flatters us or not. How this differs from the Full-Stack Engineer seat Both seats sit in the Tech Lab, both build with agents, and both own products for years. A Full-Stack Engineer works beside a Product Owner, who holds the business relationship and the roadmap, and owns the build, the architecture and the release. A Full-Stack Product Engineer holds both halves — on products small enough,



and close enough to their users, that splitting them would only slow the product down. If you want to go deep on architecture and let someone else hold the room, the Full-Stack Engineer ad is the better fit. If you care as much about whether a feature should exist as about how to build it, this one is. Every change is reviewed by an agent before a person signs it off. Every build ships tests, and the gate is 100% pass. Anything AI-powered ships with evals — a scored set of inputs, not "it looked right when I tried it". In This Seat The Risk Is Not Slow Software, It Is Fast Software Nobody Needed. Agent code compiles, passes the test it wrote for itself, and is subtly wrong in ways only someone who understands the product will catch. it is part of owning the thing, and it keeps you honest about quality. You have shipped something people used, and you watched them use it. You are comfortable across the front and the back of a web application. Strong Type Script if you have it; You can tell when a screen is making the user do the system's work, and you fix it without waiting for a designer. You use coding agents in your work and you read their output like you would a colleague's. English, fluently. It is our working language — we work across roughly fifteen countries. Spanish is genuinely useful day to day. Catalan is not required. We care what you have built, who used it, and whether you can talk us through the decisions in it. We will ask you to walk us through something you shipped and then to justify a product decision inside it — what you built, what you chose not to, and how you knew whether it worked. It is not meant to catch you out; it is how we tellproduct judgement from familiarity. A project. You decide what to build, build it, and tell us what you left out and why. You do it on your own schedule, and we go through it together afterwards.

📌 Full-Stack Product Engineer (España)
🏢 Mainloop
📍 España