Marcus Whelan
Product Lead, CheckThatPhone
I lead product at CheckThatPhone, a real-time phone number validation API for US and Canada numbers. We help developers and businesses verify carrier, line type (mobile / landline / VoIP), portability status, deliverability, and geolocation in a single API call.
Most of my day is spent at the intersection of telecom data and developer experience — figuring out what numbers actually look like in the wild (ported, reassigned, disposable VoIP), how to expose that data through a clean REST surface, and how to keep latency low when we're hitting carrier databases live instead of caching.
Topics I think about often: TCPA / HIPAA compliance for phone outreach, KYC and identity verification workflows, SMS deliverability, and fraud signals you can extract from a phone number alone. I write about these on the CheckThatPhone blog.
If you're building anything that touches phone numbers — onboarding, fraud screening, contact-list hygiene, lead validation, 2FA routing — happy to compare notes.