Senior Backend Developer

About Us CozmoX AI is building the operating system for voice-native AI employees—autonomous agents that handle sales, support, collections, and more. Backed by Y Combinator and top-tier global investors, the company is scaling rapidly across markets. About the Role We are seeking a skilled and experienced Backend Developer with 4–6 years of hands-on experience in building robust, scalable, and fault-tolerant backend systems. The ideal candidate is proficient in modern backend technologies and architectures and is excited to work in a high-growth, dynamic startup environment. This role involves working with microservices, cloud infrastructure, and modern development practices including test-driven development. Key Responsibilities Design, develop, and maintain scalable microservices using Python, Go, or Node.js. Build and maintain RESTful APIs to support web and mobile applications. Develop event-driven and asynchronous systems using Apache Kafka. Deploy and manage services using Kubernetes in AWS cloud environments. Work with SQL and NoSQL databases to store and retrieve data efficiently. Write clean, maintainable, and well-tested code following Test-Driven Development (TDD) practices. Ensure systems are fault-tolerant, scalable, and performant under load. Collaborate cross-functionally with frontend engineers, DevOps, and product teams. Participate in code reviews, architecture discussions, and team ceremonies. Continuously improve system design and development workflows. Required Skills & Qualifications 4–7 years of professional backend development experience. Proficiency in Python, Go, or Node.js (at least one language required). Strong understanding and hands-on experience with Microservices architecture. Experience with Kafka or other messaging systems (e.g., RabbitMQ). Solid understanding of both SQL (e.g., PostgreSQL, MySQL) and NoSQL (e.g., MongoDB, DynamoDB) databases. Working experience with AWS services (e.g., EC2, S3, RDS, Lambda). Hands-on experience with Kubernetes and containerized application deployment. Proven experience in writing and maintaining RESTful APIs. Commitment to Test-Driven Development (TDD) and clean coding practices. Strong debugging, problem-solving, and analytical skills. Ability to thrive in a fast-paced, dynamic startup environment. Familiarity with observability and monitoring tools (e.g., Prometheus, Grafana, ELK Stack). Nice to Have Exposure to gRPC APIs. Familiarity with Large Language Models (LLMs) and their integration into applications. Experience with Voice Technologies, such as speech recognition, text-to-speech (TTS), conversational AI Understanding of real-time streaming and event-driven systems. Why CozmoX AI Work with cutting-edge technologies in a collaborative and innovative team. High ownership, visibility, and impact on product development. Opportunity to work on scalable systems from the ground up.