Due to some uptime issues, I will need to migrate my site from my current host to another. My site is hosted on a VPS which receives lac's of mysql queries everyday. But, in future my site is definitely gonna expand, so the mysql queries. My simple question is that, can a single dedicated web server handle the mysql queries if it goes to Millions everyday ? I don't want any downtime and the performance should be optimum.
What kind of queries are there? A simple select from one table compared to queries with complex join will be very different in number. What kind of script are you using? For maximum performance MySQL specific server, I will suggest to go with Solid State Disk and a plenty of RAM, 8 GB+ But it would be best for you to consult with your host directly, give them enough details about your scripts and they will come with a solution that is suitable for your needs.
I think you should be good, but then again it may depend on the host and their servers. But really if your site is that important you should invest in hosting your own servers. Working for a shared hosting provider, I've seen sites that get about 1 million hits every few seconds last on that platform and not get shutdown for a few days. Of course it was on a static site though, but other providers might not have been able to handle that at all.