I think this is how it works: If you upgrade your package you can keep the IP; however, when you upgrade packages the disk space stays the same as what you originally purchased. There is a method to resize your disk space, but you lose your IP when you do that. I have read that DigitalOcean is working on fixing this. I’ve been here for a while and the Company does seem to take seriously what it’s users want – I’ve seen several positive changes. I figure they will get this fixed as well.

@leonardthong your IP will keep the same after the upgrade. About the 10k concurrent users you may need to create some caching platform, optimize your site/server and use services like Cloudflare.

Try Varnish4 and Cloudflare to start with, if possible get a couple of $5 droplets to load your traffic (both with Varnish installed) and make sure to use LEMP and not LAMP as the former is more efficient.

They just announced that you can upgrade your disk space if you do a “permanent” upgrade:

https://www.digitalocean.com/community/tutorials/how-to-resize-your-droplets-on-digitalocean