Full-Time

Fullstack Engineer

Updated on 8/1/2026

Onyx

Onyx

11-50 employees

AI-powered mobile trainer with form feedback

Compensation Overview

$150k - $400k/yr

+ Compensated work trial

San Francisco, CA, USA

In Person

Category
Software Engineering (1)
Required Skills
LLM
Kubernetes
Microsoft Azure
Python
React.js
Neural Networks
Postgres
RDBMS
Docker
TypeScript
AWS
Next.js
REST APIs
Google Cloud Platform

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Requirements
  • Have 1-5 years or more of software engineering experience building real-world applications.
  • Know TypeScript, React, Next.js, Python, relational databases, and PostgreSQL.
  • Be able to work in a fast-moving startup environment with low amounts of process.
  • Have excellent communication skills and a strong ability to collaborate with teammates and external customers.
Responsibilities
  • Build a consumer-grade user interface experience for the generative artificial intelligence chat, enterprise search, agents, and administration features.
  • Extend backend functionalities and application programming interfaces.
  • Improve the flexibility and quality of the search pipeline, build semantic understanding of customer organizations, extend permission and access controls, and expand knowledge curation features.
  • Implement approaches in natural language processing research, including large language model-based knowledge graphs, StructRAG, agent and deep research, to increase the range of questions the system can answer.
  • Own the entire development cycle of new features, from conception to production.
  • Collaborate with the founders and team to shape and influence product direction and contribute to engineering strategy.
Desired Qualifications
  • Experience with Docker, Kubernetes, cloud technologies such as AWS, GCP, or Azure, and on-premises or cloud deployments.
  • Experience or interest in artificial intelligence, natural language processing, deep learning, generative artificial intelligence, and information retrieval.
  • Previous experience as a founder or early engineer at a seed or Series A startup.

Onyx is a mobile AI-powered personal trainer for at-home workouts. It uses the smartphone camera to track movements, automatically counts reps, and provides real-time feedback on form to prevent injuries and improve effectiveness. It offers personalized workout plans aligned with goals like strength, muscle building, or weight loss, and it tracks progress over time. Its differentiator is real-time form correction and rep counting through computer vision, combined with integrated coaching and progress tracking in one app to support safer, more effective workouts.

Company Size

11-50

Company Stage

Seed

Total Funding

$10.1M

Headquarters

San Francisco, California

Founded

2023

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Simplify Jobs

Simplify's Take

What believers are saying

  • Private leaderboard groups with friends boost user engagement significantly.
  • Lifetime subscriptions grant unlimited access to all workouts and tracking.
  • Real-time competition via game-like matchmaking drives retention higher.

What critics are saying

  • Apple Fitness+ AI form correction locks users into ecosystem within 6-12 months.
  • Google Fit pre-installs Gemini rep counting on 2B+ Android devices in 9-15 months.
  • OpenAI GPT-5 API commoditizes camera form correction for competitors in 6-12 months.

What makes Onyx unique

  • Onyx uses smartphone camera for 3D motion capture to count reps accurately.
  • Provides real-time form correction to prevent injuries during home workouts.
  • Offers personalized programs for strength, muscle building, and weight loss.

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Benefits

Remote Work Options

Flexible Work Hours

Unlimited Paid Time Off

Paid Vacation

Health Insurance

401(k) Retirement Plan

401(k) Company Match

Wellness Program

Mental Health Support

Conference Attendance Budget

Professional Development Budget

Stock Options

Company Equity

Parental Leave

Family Planning Benefits

Fertility Treatment Support

Adoption Assistance

Phone/Internet Stipend

Home Office Stipend

Relocation Assistance

Tuition Reimbursement

Professional Certification Support

Company News

AiThority
Mar 13th, 2025
Onyx Raises $10 Million To Help Teams Find Knowledge Faster with Open Source AI Agents

Onyx, the first AI deep research agent designed for the workplace, announced today a $10M seed round of funding.

The Business Journals
Apr 3rd, 2024
Here's what you need to know about Y Combinator's 2024 winter batch demo day

Y Combinator seeded more than 250 companies in its current winter batch, which leans heavily into AI. One particular AI subcategory has nearly tripled over the past year.