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Build a mini-CRM for your small business

Contacts, deals, and follow-ups — shipped in an afternoon.

Marcus Tan Founding Engineer, Y Build
Published May 28, 2026
10 min
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A working CRM doesn’t need Salesforce. We built a focused contacts-and-deals tracker with reminders and a shared inbox view, and put it on a real domain the same afternoon.

Scope first

The trick is ruthless scope: contacts, deals, follow-ups. No more. We show the exact prompts and the schema the model landed on.

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Written by
Marcus Tan Founding Engineer, Y Build

Marcus has shipped 40+ production apps with AI tooling and runs the Build Lab experiments — the timed, reproducible head-to-heads behind every Compare and Lab note. Previously built developer platforms at two YC startups.

40+ apps shipped 8 yrs full-stack Author · The Lab
More from Marcus → @marcustan github ↗

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