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.