I have a dynamic sitemap that will change on a daily basis. Because I'm hosting on Heroku, I'm having some difficulty getting it to persist. I'm considering having the sitemap generate on request, rather than generated and saved to a static file on the server.It's a large file with tens of thousands of entries so it takes a considerable amount of time to load. Will this affect how search engines treat my site?
Does the load time of an XML sitemap matter?
sitemap;performance
All browsers have a connection timeout where they give up when waiting on your server.   For most browsers it is around 30 seconds.   I was unable to find any documentation on what the connection timeout that Googlebot uses is, but I would expect it also to be around 30 seconds.If you can keep your time to first byte under 30 seconds, I would expect that Googlebot would be able to fetch and use your dynamically generated sitemap.