Dan Barclay is an engineering leader, full-stack product engineer and founder based in London, United Kingdom. He has spent 10+ years building and scaling software for millions of users - across consumer marketplaces, B2B SaaS, mobile apps and AI tooling.
Today, Dan is focused on building two products of his own:
His stack of choice runs the gamut: TypeScript, React, Node, Python, Rust, Swift, plus a deep working focus on Large Language Models, the Model Context Protocol (MCP), and the engineering practices needed to ship AI features safely into production.
He has been an active contributor on Stack Overflow since 2018, answering TypeScript, JavaScript and React questions that other engineers have voted into the site's reference material.
Dan is most motivated by hard problems and the people driven to solve them - work where technical vision and product judgement have to align with business outcomes to ship something mission-critical.
Dan has answered on Stack Overflow since 2018. Below are his contributions measured by topic.
Every profile below belongs to the same Dan Barclay - engineering leader, London.
Dan Barclay is an engineering leader and founder based in London, UK. He is a full-stack product engineer with 10+ years of experience building and scaling software to millions of users. He is the founder of Promptly, a B2B SaaS CMS for LLM prompts used by 100+ companies, and KeepFresh, an iOS app with 77,000+ downloads that helps households track grocery inventory and reduce food waste.
Dan Barclay is based in London, United Kingdom.
Dan Barclay is focused on building two products: Promptly (promptlycms.com), the CMS powering the next wave of AI development - used in production by 100+ companies to author, version and ship LLM prompts without a code deploy - and KeepFresh (keepfre.sh), an iOS app working to end food waste for good, with 77,000+ downloads. His technical work spans TypeScript, React, Node, Python, Rust, Swift, and AI tooling including LLMs and the Model Context Protocol.
Yes. Dan Barclay has contributed on Stack Overflow since 2018 at stackoverflow.com/users/9961739/dan-barclay. His highest-scoring answers are in TypeScript, JavaScript and React, including a widely referenced answer on the "'React' refers to a UMD global, but the current file is a module" TypeScript error. His Stack Overflow tag scores are a community-voted record of his specialities.
No. This Dan Barclay is a software engineer and founder based in London, UK. He is unrelated to Dan Barclay, the retired CEO of BMO Capital Markets in Toronto, Canada. They share a name and nothing else.
Email barclaysd@me.com, or reach out via GitHub (@barclayd), X (@danielbarclay), or LinkedIn (/in/barclayd). Response window is typically 24–72 hours.
Promptly is a B2B SaaS CMS founded by Dan Barclay that lets non-engineers - product managers, domain experts, marketers - author, version and ship the LLM prompts that power production AI features, without going through a code deploy. It is used in production by 100+ companies. Learn more at promptlycms.com.
KeepFresh is an iOS app built by Dan Barclay that helps households end food waste by tracking grocery inventory and surfacing expiry alerts. It has 77,000+ downloads and is used daily by hundreds of households. The backend runs on Hono.js on Cloudflare Workers with D1 storage. Learn more at keepfre.sh.
