Senior Backend Engineer, Node.js/TypeScript

About MentionLab People used to search on Google. Now they ask ChatGPT, Gemini and Perplexity what to buy and which brand to trust, and soon AI will buy for them. MentionLab shows businesses how AI sees them: what AI engines say about their brand, how they compare to competitors, and which sources shape those answers. We're building the data and intelligence layer for AI Search and agentic commerce. Born in Brussels and global from day one, we already serve global brands directly and through leading consultancies and agencies. We're moving fast in one of the biggest shifts in how people discover information, and we're looking for people who want to build incredible things with us. The Role As a Senior Backend Engineer at MentionLab, you'll be at the heart of our data infrastructure. You'll design and maintain the systems that power our analytics platform - from ingestion pipelines to the APIs that serve insights to our users. If you love working with analytical databases at scale, building fast and reliable data pipelines, have experience with ClickHouse (OLAP), and want to own meaningful parts of a product from day one - this role is for you. What You'll Build Own our data architecture, from ingestion pipelines to ClickHouse data models, and make the key technical trade-offsDesign and optimise analytical queries and data models that stay fast as volumes growBuild and maintain the backend APIs that serve insights to our users and partnersKeep our pipelines reliable and performant in productionWork mainly in TypeScript and SQL,(with Rust) for performance-critical data processingRaise the engineering bar through code reviews, standards and mentoringWear multiple hats (because startup) The Stack TypeScript, SQL,(and Rust);NestJS with MikroORM and Knex on PostgreSQL; ClickHouse (OLAP) for analytical workloads; Redis for queue management (BullMQ + custom for high throughput). What We're Looking For Technical Requirements: 5+ years of software engineering experienceStrong, hands-on experience with data modelling, query optimisation, and performance tuningSolid knowledge of TypeScript and SQLComfortable working across both analytical and transactional databasesExperience with AI-assisted development tools (Copilot, Cursor, Claude Code, or similar) What We Value: Proactive mindset - spot issues, propose solutions, don't wait to be toldComfortable with code reviews and constructive feedbackCare about code quality but know when to ship fast Nice to Have: Experience with NestJS, PostgreSQL, RedisHosting or infrastructure knowledge (Docker / Kubernetes)Previous startup experienceReact or other frontend experience You'll Thrive Here If You enjoy figuring things out and don't need hand-holding. You're comfortable with ambiguity and changing priorities. You like collaborating and sharing what you learn. You're excited about AI and its impact on how people discover information. And you're AI-native - you don't just build AI products, you build with AI. How We Work Languages: French required. English working proficiency for documentation and some meetings. Location: Belgium-based (Brussels - Hybrid). Permanent contract (CDI) - 38h/week. What We Offer Fair salary package including car/mobility budget and insurance Dynamic workplace - Small, ambitious team A chance to shape the technological direction of the company High level of autonomy with guidance when needed - you're not alone! Important note: we hire people, not roles.If you're excited about this opportunity but don't check every box, we'd love to hear from you. This is a guide, not a checklist.