---
title: 'Backend Software Engineer at Theori'
canonical: 'https://feeny.ai/job/backend-software-engineer-theori-united-states-g0n0j5rwvavp'
type: 'job'
last_seen: '2026-09-10'
---

# Backend Software Engineer at Theori

- **Company:** Theori
- **Location:** United States
- **Employment:** full-time
- **Work type:** remote
- **Posted:** 2026-06-04
- **Last confirmed live:** 2026-09-10
- **Apply:** https://jobs.ashbyhq.com/theori/e043b073-3807-4d94-9e87-0c7d7356da18

## Job description

We’re looking for an experienced backend engineer to help build and scale the next generation of AI-driven cybersecurity platforms at Theori. You’ll play a key role in architecting and implementing core backend systems that power Xint, our autonomous penetration testing framework.

This is a foundational role in our NA engineering team—ideal for someone who thrives on solving complex systems challenges, enjoys designing for scale and reliability, and wants to help define engineering excellence in a fast-growing, AI-first company.

## Key Responsibilities

- Architect, develop, and maintain backend services and APIs that power Theori’s AI security platforms.
- Design for performance, scalability, and fault-tolerance across distributed systems.
- Collaborate with product and frontend engineers to define and deliver secure, well-structured APIs.
- Build and optimize data pipelines supporting LLM agent workflows and real-time scanning.
- Establish backend best practices, coding standards, and CI/CD processes for a growing US team.
- Write clean, well-tested, and maintainable code in Python and related technologies.
- Mentor junior engineers and contribute to a strong, collaborative engineering culture.

## Requirements

- 5+ years of professional software engineering experience building production systems.
- Strong proficiency in Python, with proven experience developing reliable backend services (FastAPI preferred).
- Solid understanding of system design, distributed architectures, and performance optimization.
- Experience with Redis, PostgreSQL, and Docker-based environments.
- Familiarity with AI/LLM-driven workflows or asynchronous, event-based architectures.
- Comfort working in an early-stage environment with evolving requirements.
- Self-directed, ownership-oriented, and comfortable driving projects from design to deployment.
- Based in US or Canada.

## Nice to Have

- Experience with Rust.
- Background in cybersecurity, application security, or vulnerability analysis.
- Knowledge of message queues, task orchestration, or microservices.
- Familiarity with LLM integration, RAG pipelines, or vector databases.
- Prior experience in startups or B2B SaaS environments.
- Previous involvement in building or scaling distributed systems or engineering teams.

## What We Offer

## Compensation & Benefits

- Competitive salary + equity
- Health, dental, and vision insurance
- Generous PTO policy
- Remote work
- Laptop + home office stipend

Engineering Culture

- Ship features that matter
- Modern Python-based stack (FastAPI, Redis, PostgreSQL, Docker)
- Strong focus on testing and quality
- Clear documentation and processes
- Collaborative, low-ego team
- Career growth and mentorship

Work-Life Balance

- Flexible hours, remote-first culture
- Focus on outcomes, not hours

## About Theori

## Company Overview
- **One-liner**: Theori is an offensive cybersecurity company that uses AI-powered solutions and elite hacker expertise to secure AI systems, applications, and networks for global clients.
- **Entity Type**: Private (Seed stage)
- **Headquarters**: Austin, Texas, United States (US office); Seoul, South Korea (Korea office)
- **Founded**: 2016
- **Founders**: Not publicly listed (company built by elite hackers with multiple DEF CON wins)

## Core Business
- **Primary industry/industries**: Cybersecurity (offensive security, AI security, application security, blockchain security, security training)
- **Target customers**: Enterprises (B2B) – including Microsoft, Google, Okta, POSCO DX; also government and defense organizations
- **Mission or purpose statement**: “Raising the standard of security at every turn” – Theori tackles the most difficult cybersecurity challenges from an attacker’s perspective and trains the next generation of security leaders.

## Products & Services
- **Xint**: AI-powered application security testing (AST) solution that identifies vulnerabilities with human-level expertise, speed, and cost efficiency. Includes Xint Code for real-time code scanning.
- **αprism**: LLM security monitoring and guard model that continuously monitors prompts and model responses to protect AI interactions.
- **Dreamhack / Dreamhack Enterprise**: Cybersecurity training platform offering interactive, self-paced learning and customizable curricula for enterprises. Includes a paid subscription service and in-house competition management.
- **PatchDay**: Bug bounty platform launched in 2024.
- **ChainLight / ChainLight DART**: Blockchain security audit and risk management services.
- **Fermium-252**: Threat intelligence database.
- **AI Red Teaming**: Expert-led audits covering all angles of AI systems to identify vulnerabilities before exploitation.
- **Relic Protocol**: Chain data attestation protocol (launched 2018).
- **Upside Academy**: Cyber training program (now in its 3rd edition).

## Market Standing
- **Valuation/Market Cap**: Not disclosed (private company)
- **Key Metric**: Total Funding – **$15.5 million** (seed round led by K2G Fund, reported in 2025); prior investment from NAVER (2020).
- **Notable Investors/Partners**: K2G Fund (lead), NAVER, POSCO DX (strategic partnership), Okta (strategic cybersecurity partnership).
- **Growth Signals**:
  - Won #1 in DARPA AI Cyber Challenge (AIxCC) Semifinals (2024)
  - 9 DEF CON competition wins
  - Over 50 international hacking competition wins
  - Beta launch of αprism in April 2025
  - Launch of PatchDay bug bounty platform (August 2024)
  - Partnership with POSCO DX for AI-driven security framework (May 2025)
  - Received Presidential Commendation from the President of South Korea (2022)
  - Opened US office in Austin, TX

## Competitive Advantages
- **Elite Hacker Team**: Built by top offensive security experts with proven track records in global hacking competitions (DEF CON, AIxCC).
- **AI-Native Security**: Products like Xint and αprism are purpose-built for the AI era, monitoring and securing LLMs and codebases proactively.
- **Offensive Security Approach**: Tests systems from an attacker’s perspective, identifying vulnerabilities before malicious actors can exploit them.
- **Trusted by Industry Leaders**: Microsoft, Google, and Okta rely on Theori’s research and solutions.
- **Dual Headquarters (US + Korea)**: Allows access to both American and Asian markets and talent pools.

## Strategic Focus
- **AI Security Leadership**: Expanding AI-powered security solutions (Xint, αprism) and AI red teaming services to address emerging threats.
- **Training the Next Generation**: Growing Dreamhack enterprise offerings and Upside Academy programs to build a skilled cybersecurity workforce.
- **Continuous Innovation**: Annual independent research period for employees and ongoing product launches (PatchDay, ChainLight, Fermium-252).
- **Global Expansion**: Building US presence from Austin office while maintaining strong Korea operations.

## Why Work Here
- **Culture Highlights**: “Built by elite hackers” – the company emphasizes hands-on hacking, continuous learning, and ethical transparency. Annual independent research period and support for CTF competitions.
- **Remote/Hybrid/Office Policy**: Hybrid workspace with two offices (Austin, TX and Seoul, Korea). Remote positions available (e.g., AppSec Engineer, Backend Software Engineer).
- **Notable Perks**:
  - Unlimited leave system
  - 1-month sabbatical leave for every 3.5 years
  - Learning stipend and education/personal development stipend
  - Technology stipend
  - Meal allowance, free snacks and drinks
  - Monthly Culture Day
  - Seasonal corporate gifts
  - Annual health screenings (Korea)
  - Support for workplace social clubs
  - Mentoring program for new recruits
  - Military service exemption business (Korea)

## Sources
1. [theori.io](https://theori.io/)
2. [theori.io/about](https://theori.io/about)
3. [theori.io/career/culture](https://theori.io/career/culture)
4. [jobs.ashbyhq.com/theori](https://jobs.ashbyhq.com/theori)
5. [builtin.com](https://builtin.com/company/theori-inc)

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