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Flex Tech Stack

HSA/FSA payment processing for eCommerce wellness brands

Financial Services San Francisco, CA 11–50 employees Founded 2023 Privately Held

Flex operates a payments infrastructure purpose-built for health savings account and flexible spending account transactions in eCommerce. The tech stack (Next.js, React, TypeScript, PostgreSQL, Redis, AWS) reflects a modern full-stack checkout service, while project focus on scalable payment infrastructure and bulk editing workflows suggests ongoing investment in merchant onboarding friction and support scaling—pain points explicitly tied to small merchants lacking processing options.

Tech Stack 13 technologies

Core StackNext.js Rust TypeScript PostgreSQL Redis AWS Slack Retool Metabase Postman React SQL JSON

What Flex Is Building

◆Challenges

Frustrating reimbursement paperwork
Small merchants lack payment processing
Scaling support function
Reducing support friction
Building scalable support systems
Limited payment processing options
Small merchants unable to process hsa/fsa payments
Onboarding and retaining partners
High volume of accounts
Structured internal processes

▲Active Projects

Hsa/fsa checkout experience
Scalable payment infrastructure
Payment integration apis
Bulk editing workflows
Data validation tools
Process documentation
Strategic named account portfolio growth
Account plan development for top targets
Cross-functional collaboration with marketing, partnerships, and product
Api integration for hsa/fsa payments

Hiring Activity

Steady6 roles · 2 in 30d

Department

Sales

3

Engineering

2

Support

1

Seniority

Mid

3

Senior

3

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About Flex

Flex provides HSA/FSA payment processing infrastructure for wellness and health eCommerce brands. The platform integrates directly into checkout flows, enabling merchants to accept tax-advantaged health spending accounts. Founded in 2023 and based in San Francisco, Flex operates as a lean, mid-stage team with technical depth (engineering and product) balanced against direct sales capacity. Core capabilities include payment integration APIs, checkout experience design, and merchant support systems.

HeadquartersSan Francisco, CA

Company Size11–50 employees

Founded2023

Hiring MarketsUnited States

Frequently Asked Questions

What tech stack does Flex use?

Flex builds on Next.js, React, TypeScript, PostgreSQL, Redis, and AWS. Backend services use Rust. Operational tools include Retool, Metabase, and Postman.