Senior Full Stack Engineer

AI is becoming the front door to discovery. People now ask ChatGPT, Perplexity, and Gemini what to buy, who to trust, and where to go; and the brands those models surface are the ones that win. MentionLab is the analytics layer for this new world: we measure how AI talks about brands, media, and institutions, benchmark them against competitors, and turn that into actions that move real visibility.

We’re a small team moving fast at the start of the biggest shift in discovery since search engines; already processing millions of data points monthly.

The Role

As a Senior Full Stack Engineer, you’ll own significant parts of our product and shape the architecture behind it. You’ll ship across the stack; APIs, data pipelines, and user‑facing interfaces – with your work leaning backend (60–70%), and you’ll set the technical bar for how the whole team builds.

This is a high‑ownership role on a small team. The systems you design and the calls you make will define what users experience and how fast everyone else can move.

What You’ll Own

• Architect and own core systems end‑to‑end; from data model to API to UI to production
• Lead on the hard problems: performance, scaling our data pipelines, and reliability under high throughput
• Set and raise the technical bar; code review standards, testing practices, technical direction
• Make architecture and build/buy decisions the team will build on for years
• Mentor other engineers
• Own frontend work independently with React when a feature needs it
• Wear multiple hats (because startup)

The Stack

TypeScript, React, SQL – and some Rust.

NestJS with MikroORM and Knex (PostgreSQL).

Redis for queues (BullMQ + custom for high throughput).

Tailwind, Shadcn.

It’s a codebase we actually care about: typed strictly, reviewed properly, and built to be maintained, not just shipped and forgotten.

What We’re Looking For

• 6+ years building and shipping production software
• Deep TypeScript and SQL; strong backend fundamentals – API design, server‑side logic, schema design
• A track record of owning systems end‑to‑end and making architecture decisions that held up under growth
• Genuinely comfortable across the stack – you can own frontend (React) when it’s the right thing to do
• Experience scaling data‑heavy systems – queues, async processing, high throughput
• You work fluently with AI dev tools (Cursor, Claude Code, Copilot) and have opinions about where they help and where they don’t

What We Value

• Proactive by default – you spot issues, propose solutions, and don’t wait to be told
• You raise the level of the people around you through reviews, pairing, and clear thinking
• You care about quality but know when to ship fast

Nice to Have

• ClickHouse or other analytical / columnar datastores
• Previous startup or founding‑engineer experience

You like figuring things out and don’t need hand‑holding. You’re comfortable with ambiguity and shifting priorities. You enjoy sharing what you learn. You’re excited about AI’s impact on how people discover everything – and you’re AI‑native: you don’t just build AI products, you build with AI.

Languages: French highly preferred. English working proficiency for documentation and some meetings.

Location: Belgium‑based (Brussels – depending on the profile we’re open to remote/partial remote). Permanent contract (CDI) – 38h/week.

What We Offer

• Fair package, plus car/mobility budget, meal & eco vouchers, and hospitalization insurance
• A real seat at the table on the company’s technical direction
• High autonomy – with guidance when you want or need it. You’re not alone.
• A young, ambitious team and a product at the frontier of a brand‑new category

Interview Process

1. Quick online chat – 30 min
2. Deep‑dive technical discussion (preferably on‑site with Martin) – 1 hour

We hire people, not roles

Excited but don’t tick every box? Still write to us; this is a guide, not a checklist.

Interested? Send your CV to [email protected] (a GitHub or a code snippet optional but appreciated).