Staff Software Engineer, Flex
AI Platform
$170-250k
Salary varies depending on location. Offers equity
Flexible rent payment application
Be an early applicant
Flexible rent payment application
501-1000 employees
Be an early applicant
$170-250k
Salary varies depending on location. Offers equity
501-1000 employees
Company mission
To help people pay for the things that matter most.
Role
Who you are
- 6+ years of experience in software development or a related field, with at least 2+ years building production AI or agentic systems
- Experience in technical leadership, guiding engineering teams through complex projects
- Hands-on experience with coding CLIs and AI dev tools (Claude Code, Codex, OpenCode, Cursor, or equivalents) - both as a daily-driver user and as a builder integrating them into team workflows
- Experience with agent infrastructure and code-execution sandboxes (Modal, E2B, Cloudflare Sandboxes, Daytona, or Firecracker/gVisor-based runtimes), with a clear point of view on isolation, scaling, and cost trade-offs
- Experience building AI-first workflows end-to-end, including LLM application design, prompt and context engineering, RAG, and human-in-the-loop patterns
- Experience creating and managing agents and agent platforms, including multi-agent orchestration (LangGraph, custom planners, sub-agent patterns), tool/skill registries, and MCP-based integrations
- Experience with eval frameworks and offline/online evaluation of agent quality, plus observability and tracing for non-deterministic systems
- Experience with Java, Python, Golang, or TypeScript/Node.js
- Strong experience with relational SQL and NoSQL databases, such as MySQL/PostgreSQL/DynamoDB
- Experience designing and developing fault-tolerant and scalable distributed systems, including workflow and job-orchestration engines
- Experience with AWS cloud services: ECS/EKS, Lambda, API Gateway, VPC, RDS, etc
- Infrastructure as code (AWS CLI, AWS CDK/Terraform)
- Strong communication skills with the ability to understand and explain technical issues to a non-technical audience
- Follow engineering best practices as well as propose new ones - especially around responsible AI use, guardrails, and security for agentic systems
- Bonus: experience with model and prompt evaluation tooling, secure tool-use sandboxing, retrieval and vector stores, and operating multi-tenant AI platforms at scale
What the job involves
- Flex is looking for a Staff AI Engineer to join our AI Central Team and help us transform the way we work by building the tools and capabilities that support AI-first workflows across Flex
- As a Staff AI Engineer at Flex, you’ll help set technical direction and shape the long-term architecture of the AI systems and tools that all departments use to power their agentic workflows
- You will own AI platform features and capabilities end-to-end including analysis, planning, implementation and production rollout to our internal customers
- You’ll work closely with your AI Central Team peers and consult with department leads to anticipate business needs and proactively build the AI capabilities to address them
- You’ll also play a critical role in mentoring, elevating technical standards, and ensuring the success of our Flex’s transformation into an AI-first organization
- Design, implement, and maintain the agent platform including orchestration, tool execution, sandboxed code runtimes, observability, and the developer-facing SDKs and UI
- Design and develop new APIs, SDKs, and developer surfaces that let other teams onboard agents quickly and safely, with strong defaults for evals, guardrails, human-in-the-loop review, and audit
- Scale the platform to support a growing catalog of agents, skills, and MCP integrations across Flex while maintaining performance, reliability, and cost efficiency
- Continuously improve our daily operations with automation, tooling, design evolution, and observability, including agent-trace visibility, evaluation pipelines, and sandbox runtime monitoring
- Work closely with cross-functional teams to identify high-leverage AI use cases and turn them into production-ready agents on the platform
- Set the bar for AI-assisted engineering practices and responsible AI use across Flex, mentor engineers on how to design, build, and operate agentic systems, and bring outside innovation back into our roadmap
Our take
Many people struggle to pay their rent every month, with a variety of bills hitting their bank accounts simultaneously. Whilst many of these people earn enough money to cover their bills, the inflexible nature of monthly bills can make the all-in-one payment a harder obstacle.
Flex provides a mobile application for the flexible payment of rent, allowing users to pay their landlords through flexible payment plans, reschedule payments when necessary, and protect their funds through Overdraft Protection. The company achieves this by partnering with estate agents and paying their resident's bills upfront, taking on the challenges that landlords would normally have due to late payments.
Flex has experienced extremely rapid growth since its founding which has caused some issues, as it struggled to keep up with the surge in new customers. Having made improvements to its product and scaled its customer service team, it is set to continue providing a service that has come to be highly valued by both tenants and landlords.
Freddie
Company Specialist at Welcome to the Jungle
Insights
10% employee growth in 12 months
Company
Funding (last 2 of 5 rounds)
Feb 2022
$160m
SERIES C
Apr 2021
$46.6m
SERIES B
Total funding: $225.1m
Company benefits
- Medical, Dental & Vision: Your healthcare will be available from Day 1— giving you immediate peace of mind — with best in class coverage and options.
- Parental Leave: Step away with paid time off to focus on family and life’s newest chapter.
- NYC HQ: Collaborate in our lively New York headquarters, with new office space on the way!
- 401(k) Retirement Savings: Plan ahead with our 401(k) program to grow your future. And starting early 2026, employees will be eligible for a company match!
- Flex Giving: Flex Giving empowers employees to support local nonprofits advancing housing stability in the communities we call home.
- Employee Assistance Fund: Confidential financial support to teammates facing unexpected hardships or emergencies.
- Hybrid Work Policy: Work flexibly from home, with in-person collaboration and events that matter.
- Unlimited PTO + Holidays: Take the time you need— whether that’s a vacation, recharge, or simply a long weekend
- Free Flex Subscription: As a Flex employee, you'll have full access to our services without charge.
- GrubHub Credit: Enjoy meal credits while in the office, so you’re fueled for the workday ahead.
Company HQ
Midtown Manhattan, New York, NY
Leadership
Shragie Lichtenstein
(Co-Founder & CEO)Prior to co-founding Flex in 2019, Shragie co-founded Boundless Reality. They graduated from Yeshiva University in 2015 with a Bachelor's Degree in Finance.
YeTong Shao
(Co-Founder)Prior to co-founding Flex in 2019, YeTong co-founded Boundless Reality alongside Shragie. They graduated from the University of Chicago with a Bachelor's Degree in Mathematic & Economics.
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