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Senior Full Stack Engineer - Agentic AI Startup

NinjaTech AI
Mountain View, CA Full Time
POSTED ON 12/24/2025
AVAILABLE BEFORE 1/22/2026
We invite you to join NinjaTech AI as a Senior Full Stack Software Engineer as we're building the future of autonomous AI agents: our technology that doesn't just assist, but actually executes complex tasks end-to-end.

Why this opportunity is exciting:

  • First FE-Leaning Engineer at HQ: you will work side-by-side with expert-level Full stack engineers
  • Founding Team Impact: Work directly with our mostly ex-AWS founding engineering team and ex-Google Product/UX leaders
  • Cutting-Edge AI: Build infrastructure, OS and UI for autonomous AI agents that can actually do things end to end
  • High Velocity, High Impact: Ship features that millions of users will interact with (B2C and B2B)
  • Technical Ownership: Own significant parts of the product architecture and make decisions that will scale with the company!

About the Company:

NinjaTech AI is a generative AI startup (B2C and B2B) with headquarters in Silicon Valley and offices in Sydney and Vancouver. Our team built an Agentic AI product from the ground up: we use cutting edge tools and do a lot of innovative work, while prioritizing fast iteration and quick delivery. Our flagship product, SuperNinja, is an advanced agentic AI platform with full OS capabilities, performing website creation, end-to-end coding, advanced data analysis, and more. NinjaTech AI is backed by Alexa Fund and Samsung Ventures and we are on track to raise Series A funding.

About the Role:

The Senior Full Stack Engineer is a full-time position, based at our HQ office in Los Altos, California (5 days on-site; great office space, free daily meals). Our team works in a fast-paced and collaborative environment. We get a lot done when we ideate together and iterate quickly.

As a Senior Engineer, you'll architect and build the core user-facing features as well as back-end infrastructure that make our autonomous AI agents accessible, fast and powerful. You will report to the VP of Engineering and will collaborate on a daily basis with the founder/CEO and the VP of Product.

What you will build:

As a key member of our engineering team, the Senior Software Engineer will be responsible for translating our vision and customer needs into functional and appealing interactive applications, ensuring a great user experience.

  • Develop and implement serving architecture for our distributed systems with focus on scalability, observability, and efficiency
  • Design and build components for internal SDKs for microservices and integrate them in collaboration with other developers
  • Write robust and well-documented code, ensuring quality through automated testing and continuous integration and deployment
  • Work effectively in a fast-paced, dynamic team environment, contributing to multiple projects
  • Conduct code reviews and provide constructive feedback to other members of the team
  • Develop and maintain documentation for the platform, including API documentation, technical guides, and technical specifications
  • Explore new tools and technologies that can improve development efficiency and product quality

Required Experience:

  • 5 years of experience in software development, with a focus on building scalable and reliable web applications.
  • Expert-level experience in React.
  • Proficiency in Next.js and Python.
  • Experience with AWS Cloud.
  • Strong expertise in various API protocols, including RESTful API and WebSockets.
  • Familiarity with database technologies such as Firebase, Supabase, DynamoDB, NoSQL, PostgreSQL, or MySQL.
  • Hands-on experience in building microservices for service-oriented architecture (SoA) on top of AWS services, leveraging various components (e.g., SQS, Lambda, SNS, ECS, etc.).
  • In-depth understanding of the entire web development process (design, development and deployment).
  • Familiarity with RESTful APIs and integration of backend services.
  • Knowledge of version control systems (e.g., Git) and experience working with collaborative development tools.
  • Ability to perform well in a fast-paced environment where deadlines are tight and priorities can change rapidly.
  • Strong problem-solving skills and ability to work in a team environment.

Preferred Qualifications:

  • Bachelor's or Master's degree in Computer Science or Engineering
  • Experience with Large language models (LLMs) and AI agent frameworks, as well as machine learning model deployment and serving
  • Knowledge of real-time systems and WebSocket/streaming protocols
  • Experience with infrastructure as code (CDK, Terraform, CloudFormation)
  • Experience in a high-growth startup environment
  • Experience with observability tools (Grafana, DataDog)

Benefits:

  • Excellent Health insurance plans
  • 401(k)
  • Generous Paid Time Off (Vacation, Sick & Holidays)
  • Paid meals and snacks
  • Equity grants (we are still pre-Series A so it's a great time to join the founding team!)

Compensation Range: $160K - $190K

Salary : $160,000 - $190,000

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