We moved to caddy as a front end for our unlimited domains offering after some experimentation[0]. ALBs didn't work at the scale we needed them to, so we run our own caddy instances.

Seems to work great. We did run into a rate limiting issue with letsencrypt when we tried to provision too many certs at one time. Ended up having to use wildcard certs to decrease the number of requests. Hardly caddy's fault, though.

0: https://fusionauth.io/blog/unlimited-domains-fusionauth