Software Development Engineer III - Users

About Lumen Dynamics : Lumen Dynamics is an AI-powered business operating system that gives agencies, entrepreneurs and SMBs the infrastructure to build, automate and scale. Today, Lumen Dynamics supports SMBs across 150+ countries, fueling community-driven growth rooted in real customer outcomes. To date, businesses operating on Lumen Dynamics have generated over $7 billion in ecosystem value, demonstrating the impact of shared infrastructure at scale. By centralizing conversations, automation and intelligence into one system, we help businesses move faster, reduce complexity and execute efficiently. Behind the platform, Lumen Dynamics powers more than 4 billion API hits and 2.5 billion message events daily. With 250 terabytes of distributed data, 250+ microservices and over 1 million domain names supported, our architecture is built for performance, resilience and long-term scalability. Our people With over 2,000 team members across 10+ countries, Lumen Dynamics operates as a global, remote-first organization built for speed and ownership. We value initiative, clarity and execution, creating space for ambitious people to build systems that support millions of businesses worldwide. Here, innovation thrives, ideas are celebrated and people come first, no matter where they call home. Our impact Every month, Lumen Dynamics enables more than 1.5 billion messages, 200 million leads and 20 million conversations for the more than 1 million businesses we support. Behind those numbers are real people building independence, expanding opportunity and creating measurable impact. We’re proud to be a part of that. Learn more about us on our YouTube Channel or Blog Posts About the Role We’re looking for a seasoned Senior FullStack Engineer (SDE III) to join our Users Module team, where you'll design and build scalable, secure user management systems. This includes working on authentication, authorization, and complex permission hierarchies across a multi-tenant SaaS platform.You’ll collaborate cross-functionally to deliver reliable, performant, and secure experiences for millions of users. This role is ideal for someone who thrives in product-oriented backend systems, has a strong full stack foundation, and is comfortable using AI tools to enhance their development speed and effectiveness. Responsibilities: Write clean, maintainable code in TypeScript/JavaScript Build and maintain robust RESTful APIs for user management and authentication Design scalable multi-tenant user data models and schemas Implement OAuth, JWT, and secure session management Design and implement IAM v2 systems with RBAC and granular permissions Build features like user impersonation, delegation, and permission templates Create and manage token validation and session lifecycle flows Architect scalable models using MongoDB, Firestore, and SQL Integrate Elasticsearch for advanced user search and filtering Sync user data across multiple stores and implement audit logging Build secure auth flows with encryption, token validation, and data privacy controls Ensure compliance with GDPR and similar regulations Create audit trails and compliance reporting for user actions Optimize queries, implement caching strategies, and handle high-volume user operations Build systems that scale across enterprise-grade customer environments Partner with product, security, and platform teams to deliver features Collaborate with DevOps on deployment and infrastructure Mentor junior engineers and participate in architecture discussions and code reviews Required Candidate Profile: 4+ years in backend engineering, preferably building user management systems Proven work on authentication/authorization and IAM systems Experience with multi-tenant SaaS and enterprise user workflows & permissions Required Technical Skills Languages: TypeScript, JavaScript, Node.js Frameworks: NestJS, Express.js Databases: MongoDB, Firestore, SQL Authentication: OAuth 2.0, JWT, session management Cloud: Google Cloud Platform (GCP) Messaging: Google Cloud Pub/SubDevOps: Git, CI/CD Search: Elasticsearch, Clickhouse Architecture: Microservices, Event driven architecture, IAM, RBAC EEO Statement: The company is an Equal Opportunity Employer. As an employer subject to affirmative action regulations, we invite you to voluntarily provide the following demographic information. This information is used solely for compliance with government recordkeeping, reporting, and other legal requirements. Providing this information is voluntary and refusal to do so will not affect your application status. This data will be kept separate from your application and will not be used in the hiring decision. EEO Statement: The company is an Equal Opportunity Employer. As an employer subject to affirmative action regulations, we invite you to voluntarily provide the following demographic information. This information is used solely for compliance with government recordkeeping, reporting, and other legal requirements. Providing this information is voluntary and