I have been looking for a hosting solution that can support at least 500 users at once. Could someone propose an excellent choice or offer tips on what to look for in a hosting service for this kind of traffic? Thanks!

Pretty much all the providers nowadays come with a money back guarantee. So you are free to explore different web hosts and pick the best.
Can recommend Greenhost.cloud eco-friendly hosting to those who want a stable, fast provider.
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For high-traffic websites with 500+ concurrent users, consider cloud-based solutions like Amazon Web Services (AWS), Google Cloud Platform, or DigitalOcean. These scalable services offer robust infrastructure, load balancing, and flexible resources to ensure optimal performance and reliability.

Give Profvds.com cheap vps a try. They offer very good value for money. Everything is running very well.
Speed connectivity is quite good. Customer support is responsive - they have professional team - I like it.

Have a look at accounts from decent hosting providers: planethoster.com and legionbox.com.
The quality of the service has consistently exceeded my expectations from the start, demonstrating both impeccable performance and reliability. The customer support, in particular, deserves commendation.

Why not give Planethoster.com a try?
Definitely some of the best Customer Support available. Support can be reached through MSN for immediate assistance, and through tickets/email which they respond to in a matter of minutes.

For handling 500 users simultaneously consider using AWS or Google Cloud for their robust scalability, reliability and performance. Both offer excellent support for high traffic applications.

I would recommend you to start your search here: https://allwebhost.com/dedicated-servers/
They have a lot of dedicated hosted solutions.