How I migrated magic-link login from Resend to AWS SES + Lambda five days before launch (opens in new tab)

I run toui.io, a URL shortener I shipped to the public on April 7, 2026. Eleven days before launch I had passwordless email login working on Resend. Five days before launch I tore it out and rebuilt the same flow on AWS — Lambda + DynamoDB + SES + API Gateway, packaged as a SAM stack. The whole migration took one afternoon. I want to write about why I did it, what the stack looks like, and the one thing I'd do differently. This isn't a Resend hit piece. Resend is excellent for product enginee...