Principal FullStack Engineer

At Experis, a ManpowerGroup company, we specialise in recruiting the best tech talent and matching them with all kinds of organisations, from large corporations to start-ups.
We are a company specialising in IT consultancy and the recruitment of professionals in the technology sector across our three practice areas: Business Transformation, Cloud & Infrastructure, and Enterprise Applications.
We have a workforce of over 1,800 IT specialists in Spain and an international presence in 54 countries.
If you’re a technology professional, we’d love to help you find that new opportunity you’re looking for – the one that will help you take the next step in your career.
Find your next opportunity with us. Take your career to the next level with Experis.
About the role
A small, experienced group of engineers, a designer and a founding team that stays close to the product. Engineers
own features end to end, work closely with design, and have a direct line to the decisions that matter. We use Claude
Team Enterprise as a core part of how we work and expect everyone on the team to do the same
We are a lean team of senior full-stack engineers, and this role sits at the top of that group as the person we rely on
when something is hard, ambiguous, or nobody else has the context.
This is a hands-on role, roughly 90% coding. We are not looking for a pure architect or someone who wants to direct
from a distance. We are looking for someone who is deep in the codebase every day, ships features themselves, and
makes pragmatic calls that move the product forward. You will also help shape technical direction, work directly with our
founders to turn product ideas into scoped, shippable work, and raise the bar for the whole team.
What you will own
● End-to-end feature delivery across the whole stack: Next.js frontend, Node.js backend, PostgreSQL, and
deployment.
● Our real-time analytics dashboard, which gives merchants a single view of ad performance across every
channel and platform.
● Our UI component library: long-term ownership of how we build and maintain frontend consistency across the
product.
● Infrastructure and reliability: database optimisation, Redis stability, observability, and integrations with ad
platforms including Meta, Google, Bing, and Taboola.
● Keeping the product's data layer fast and reliable as we grow: schema and query performance, sensible
aggregation, and reporting that holds up under load.
What we are looking for
Must have
● Ability to own a product end to end. We care about demonstrated depth and ownership, not the number.
● Strong TypeScript on both sides: React/Next.js on the frontend and Node.js on the backend.
● Solid PostgreSQL: schema design, query optimisation, and migrations, with the instinct to reason about
performance under high write volume.
● Experience maintaining a component library or design system, not just consuming one.
● A genuine end-to-end ownership mentality, from technical design through implementation to deployment, and
the pragmatism to ship a good solution rather than chase a perfect one.
● Comfortable making product-facing decisions with limited spec, and translating a rough founder request into
something shippable.
● Strong written communication. We are async-first and clarity matters.
● Comfortable using AI tools such as Claude as part of your daily workflow to increase speed and quality.
● Experience in a small team where you wear multiple hats.
Nice to have
● Ad tech or e-commerce background.
● GraphQL.
● Fastify or similar Node.js frameworks.
● Redis.
● DigitalOcean App Platform or Vercel.
What We Offer
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● Full-time remote with flexible hours (CET timezone overlap required)
● Competitive salary
● Claude Team Enterprise access from day one
● Direct influence on technical decisions
● A product used by thousands of real merchants every day