Another thing to think about with LE at scale, especially if you plan to renew your certs around the same time (rather than staggering them), is to make sure yo

Another thing to think about with LE at scale, especially if you plan to renew your certs around the same time (rather than staggering them), is to make sure you don't run into rate-limiting problems. In fact, if you have a REALLY major deployment (probably more than the 3,000 domains discussed here) you should work directly with the LE team to make sure that their infra is ready for you and to work out a reasonable rate of API usage between you. I know this was the experience of at least one major web hosting provider when they began offering automated LE certs for customer sites and the LE team was very accommodating.