Senior Full Stack Developer

Cognativ; United States; Remote; USD 140,000 - 200,000; Full time

Job summary

Cognativ is seeking a senior full-stack engineer to design robust C#/.NET back-ends and modern React/Next.js UIs. You will own domain modeling, API design, and asynchronous processing within an Azure-based, modular monolith.

You'll contribute across the stack, ensure testability and maintainability, and mentor other engineers while delivering customer- and operations-facing applications.

Qualifications

• 8+ years of professional software development experience.
• Strong backend design in C#/.NET (ASP.NET Core).
• 4+ years building production front-end apps with React/Next.js.
• Experience with relational DBs and ORMs (EF Core).
• Proficient TypeScript and monorepo package usage.
• Cloud infra experience (Azure preferred).
• Experience with OAuth2/OIDC authentication.
• Solid automated testing discipline (unit/integration/contract).
• Full-stack development across API, UI, and data models.
• Collaborate on API contracts and shared TS types.

Responsibilities

• Design and build clean, testable backend architecture (Clean Architecture).
• Develop and maintain multiple Next.js/React apps for internal and external users.
• Build and maintain asynchronous background processing services and message-queue coordination.
• Model relational data and implement data access with EF Core/PostgreSQL.
• Collaborate on API contracts and shared TypeScript types for front-end teams.
• Mentor engineers and participate in code reviews and design discussions.

Skills

C# / .NET

ASP.NET Core

React

Next.js

TypeScript

Azure

OAuth2 / OIDC

CI/CD

Unit & integration testing

Domain-driven design

Education

Bachelor's degree in Computer Science

Tools

EF Core

PostgreSQL

SQL

Azure DevOps

Message Queues

Blob Storage

Job description

About the role:

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.

• 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.
• 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.