Senior Fullstack Developer

COGNATIV•,

1d•Onsite

About The Position

We are building a greenfield, document-driven lending platform that automates the full lifecycle of a loan application — from document intake and OCR-based extraction, through human-in-the-loop review, to final approval and downstream submission. The system is a modular monolith with a clear separation between backend services and multiple trust-boundaried web front ends, deployed natively on Azure. We're looking for a senior full-stack engineer who is equally comfortable designing clean, testable back-end architecture in C#/.NET and building modern, production-grade UI in React/Next.js. You'll work across the stack: domain modeling, API design, background/async processing, and customer- and operations-facing web applications.

Requirements

8+ years of professional software development experience, with deep expertise in C# / .NET (ASP.NET Core).
4+ years building production front-end applications with React, including Next.js (App Router, server components/actions, route handlers).
Strong understanding of Clean/Layered Architecture, domain modeling, and separation of concerns in non-trivial back-end systems.
Experience with relational databases and ORMs (EF Core or equivalent), including migrations and query performance.
Solid TypeScript skills and comfort working in a monorepo with shared, versioned internal packages.
Experience with cloud infrastructure (Azure preferred; AWS/GCP equivalents considered) — messaging/queues, object storage, secrets management.
Experience implementing or integrating OAuth2/OIDC-based authentication, ideally with enterprise identity providers (e.g., Microsoft Entra ID or similar).
Strong automated testing discipline: unit, integration, and contract testing on both back end and front end.
Comfortable working across the full stack without hand-offs — from database schema to API to UI.
Excellent communication skills and experience working in a small, senior, high-autonomy engineering team.

Responsibilities

Design and build business logic and domain modules in an ASP.NET Core API following Clean Architecture principles (Domain, Application, Infrastructure, API layers).
Build and maintain asynchronous background processing services (a .NET worker) for document-heavy workflows, coordinated through message queues.
Develop and maintain multiple Next.js/React applications serving different user populations (internal operations/back-office tooling and external/customer-facing portals), sharing a common package layer.
Design relational data models and write efficient data access code (EF Core / PostgreSQL).
Integrate with cloud-native infrastructure: message queues, blob storage, secrets management, and managed identity providers.
Implement authentication and authorization across multiple identity boundaries (workforce vs. external/customer identity).
Collaborate on API contracts and shared TypeScript types consumed by front-end applications.
Participate in architectural decisions that keep a growing monolith modular, maintainable, and well-tested (unit, integration, contract, and architecture tests).
Work within a human-in-the-loop product model: build tooling that lets operators review, correct, and approve AI-assisted extraction results, with full traceability of how each data point changed from raw intake to final approval.
Write and maintain automated tests across the stack and participate in CI/CD pipeline health.
Participate in code review, technical design discussions, and mentor less experienced engineers.