Charles Yoo-Naut

Charles Yoo-Naut is a software engineer, product manager, and entrepreneur with a background in technology, product development, and startup building. He is the Co-Founder and CTO of Rain, and previously held engineering and product roles at Intuit and Microsoft and co-founded Playbook HR.  ^[8]

Education

Yoo-Naut graduated from Stanford University with a Bachelor of Science in Computer Science in 2012.  ^[1]

Career

Yoo-Naut began his career as a Research Intern at the Columbia University Center for Computational Learning Systems, where he worked on a machine learning project for ConEdison focused on anomaly detection in electric grid data. He later worked as a Trading Strategist Intern at Morgan Stanley, developing a project management system in C# for the Fixed Income Division, followed by software engineering internships at Togetherville and Meebo, where he worked on application development, technical planning, front-end features, and A/B testing. In 2008, he co-founded myCollegeSTAT, a college admissions platform built around user-submitted data, where he led website development, managed its infrastructure and social media presence, and helped grow its user base to thousands. From 2010 to 2012, he was a Research Assistant with the Stanford Computer Science Department's logic group, developing a JavaScript program using computational logic to manage graduate course requirements and contributing to the Stanford Intellectual Property Exchange. During the same period, he served as President of the Business Association of Stanford Entrepreneurial Students, leading a student organization of more than 100 members and overseeing entrepreneurship programs.

Yoo-Naut joined Microsoft as a PM on the Bing core search relevance team, where he worked on triggering, metrics, measurement, and editorial functions for the navigational query experience. He later co-founded Playbook HR, an HR platform for contractor workforces that automated processes including communications, background checks, electronic signing, and scheduling. After Intuit acquired it in 2015, he joined Intuit as a Principal Software Engineer, where he launched Intuit Workforce from Playbook HR and helped develop the product internally. He also served as a technical lead for QuickBooks Self-Employed, working on front-end infrastructure, bank data, billing, and TurboTax integration. From 2020 to 2022, Yoo-Naut was an Investment Scout at Lightspeed Venture Partners, where he identified and evaluated potential investment opportunities.

Since 2021, Yoo-Naut has served as Co-Founder and CTO of Rain, where he leads the company's technical development and engineering efforts. ^{[2] [3]}

Interviews

Rain

In a March 2026 interview with Stableminded, Yoo-Naut discussed Rain's growth and its development of stablecoin-based card infrastructure. He described Rain's expansion into stablecoin-first neobanks, remittance providers, and global platforms, noting that its infrastructure supported faster payouts and lower-cost transactions across multiple markets. Yoo-Naut explained that Rain used modular integrations with wallets, payment ramps, banking rails, and card programs, while improving documentation, SDKs, demos, and AI-assisted onboarding to reduce implementation times. He also discussed the company’s use of AI for compliance and customer support, while arguing that stablecoins and traditional card networks were increasingly converging as stablecoin settlement became part of card payment infrastructure. Yoo-Naut further described potential applications for agent-based payments, including temporary or tokenized cards, while noting that customers would remain responsible for transactions and that existing KYC requirements would continue to apply.  ^[7]

Mainstream Stablecoins

In a March 2026 interview at Endeavor Week 2025 alongside Farooq Malik, Yoo-Naut discussed stablecoin infrastructure development and the company’s growth since its 2021 founding. The founders described how traditional payment and payout systems can reduce workers’ earnings through conversion fees and other costs, particularly for people working remotely in countries with volatile local currencies. They discussed improvements in blockchain infrastructure, wallets, and stablecoin use cases that had supported adoption, as well as the potential for clearer regulation to provide greater certainty for companies developing stablecoin-based financial services. Yoo-Naut and Malik also described how stablecoin rails could reduce the cost and capital requirements of financial services, with a potential shift from connecting stablecoins to existing payment networks toward direct wallet-to-wallet transactions. They further discussed programmable money, AI-agent payments, and blockchain-based tools for tracking and governing transactions, while describing Endeavor’s international network as a source of relationships and opportunities for Rain's expansion into new markets.  ^[6]

Everyday Payments

In a February 2026 interview on The Investment Memo, Yoo-Naut and Malik discussed Rain's origins and development. They explained that their earlier company, Signwire, exposed them to the speed and traceability of USDC transactions when an international investment arrived within minutes, but they found that stablecoins were difficult to use for ordinary business purchases, which led to the creation of Rain. The company initially focused on corporate cards and later shifted toward providing the underlying card, blockchain, and settlement infrastructure as customers sought to build their own consumer and business products. Yoo-Naut and Malik described Rain's approach to settling transactions across different blockchains and stablecoins without requiring users to manage tokens or gas fees, with a longer-term goal of supporting programmable money movement globally. They also discussed keeping the team lean, hiring for traits like agency and curiosity, aligning employees around shared goals, and pursuing partnerships and acquisitions that strengthened the platform and customer experience. The founders attributed Rain's development to sustained customer demand, clear roles, frequent communication, and a focus on customers with immediate needs rather than treating general interest as evidence of adoption. ^[4]