Lumnix

Senior Fullstack Engineer

 

About the Client

Global FinTech startup,  is building a modern financial intelligence platform that helps teams analyze performance, forecasts, and operational metrics across time. The product is data-heavy, highly interactive, and correctness-driven. Accuracy, transparency, and trust are core principles.

We are early-stage but live, with real customers and real financial data. We move fast, but we do not break fundamentals.
 

Role Overview

We are looking for a Senior Fullstack Engineer to help design, build, and evolve core product functionality across frontend, backend, and data layers.

This is a hands-on role with real ownership. You will work closely with Product, QA, and other engineers to deliver features end-to-end, from API design to UI behavior to data correctness.

This role is not about managing people. It is about shipping high-quality software in a complex, data-driven environment.
 

What You Will Do

  • Design and build end-to-end product features, from UI to backend logic to database interactions
  • Implement and evolve core workflows, including:
    • Data ingestion and connector management
    • Metrics configuration and overrides
    • Time-based grouping (daily, weekly, monthly, quarterly, yearly)
    • Forecasting, reporting, and analytics views
  • Design, build, and maintain NestJS-based backend services and integrations, including API endpoints, domain logic, data validation, and integration workflows
  • Work within a modular monolith backend, contributing to shared domain logic and internal service boundaries
  • Write efficient, readable SQL for data retrieval, aggregation, and validation
  • Ensure correctness of financial calculations and aggregations
  • Collaborate closely with:
    • Product on requirements and edge cases
    • QA on testability and bug resolution
    • Other engineers on architecture and code quality
  • Review code and contribute to technical standards and best practices
  • Participate in release planning and production readiness
     

Required Skills & Experience

  • 5+ years of professional software engineering experience
  • Strong experience building fullstack web applications
  • Strong backend experience with Node.js-based API services, including business logic and data validation
  • Strong SQL skills (required):
  • Solid frontend experience with:
    • React
    • TypeScript
    • Modern component-based UI patterns
  • Writing complex queries
  • Aggregations and joins
  • Reasoning about data correctness and performance
  • Experience working with relational databases (PostgreSQL preferred)
  • Comfort working in production systems with real users and data
  • Ability to reason about edge cases, failure modes, and data consistency
     

Nice to Have

  • Experience with financial, analytics, or reporting platforms
  • Familiarity with React-based frontends
  • Exposure to PostgreSQL or similar relational databases
  • Experience working in early-stage or startup environments
  • Exposure to Python is a plus, but the core backend is implemented in Node.js
     

What Success Looks Like in the First 90 Days

  • You understand client’s data model and core product flows
  • You ship multiple production features end-to-end
  • Your code is readable, testable, and trusted by the team
  • You proactively surface edge cases and data issues

Product and QA rely on you for clarity and execution
 

Required languages

English C1 - Advanced
Analytics, Business Intelligence, Startup Experience, Python
Published 16 January
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