How do Wix and Squarespace manage their SSL certs?

Hey guys, a friend recommended me to post here to ask about what the best practice is for managing huge amounts of SSL certs for a CDN outside of our cloud service.

I currently run a SaaS that's similar to things like Wix, Squarespace, etc. and want to change CDNs from CloudFront as soon as possible due to their pricing. However, we realised that issuing and managing SSL certs at the scale we want would be a huge problem.

How do players like Wix/Squarespace do this?