Flex · 3 weeks ago
Staff Software Engineer, AI Platform
United States
Full-time
Remote
Lead/Staff
$200K/yr - $250K/yr
6+ years expFlex is a growth-stage FinTech company headquartered in NYC, focused on transforming the rent payment experience. They are seeking a Staff AI Engineer to lead the development of AI systems and tools, ensuring a seamless integration of AI capabilities across various departments.
AppsPaymentsFinanceFinTechSoftwareBillingFinancial Services
Responsibilities
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
Qualification
Required
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
Preferred
Bonus: experience with model and prompt evaluation tooling, secure tool-use sandboxing, retrieval and vector stores, and operating multi-tenant AI platforms at scale
Benefits
Competitive medical, dental, and vision
Company equity
401(k) plan with company match
Unlimited paid time off + 13 company paid holidays
Parental leave
Free Flex subscription
Competitive compensation + company equity
Unlimited PTO
Company
Flex
Flex enables people to pay rent bills on a schedule that fits their personal finances.
201-500 employees
H1B Sponsorship
Flex has a track record of offering H1B sponsorships. Please note that this does not
guarantee sponsorship for this specific role. Below presents additional info for your
reference. (Data Powered by US Department of Labor)
Distribution of Different Job Fields Receiving Sponsorship
100%
Represents job field similar to this job
Engineering and Development
Trends of Total Sponsorships
*2025 (1)
2024 (1)
Funding
Current Stage
Growth StageTotal Funding
unknown2025-03-31Series A
2019-11-01Seed
2019-07-24Pre Seed
Leadership Team
Shragie Lichtenstein
Co-Founder & CEO
Jeff Wang
Chief Technology Officer
Recent News
2026-06-18
2026-06-16
2026-03-25
Company data provided by crunchbase