alxuta

By using this plugin you’ll be able to allow only a specific number of visitors to navigate through your website. 
The extra influx of visitors will be kept in a virtual queue until a new space will be available.
You could always use the following shortcode [virtual-queue-position], in order to display the current user position into the queue.
Installation
<ol>
<li>Upload the <code>virtual-queue</code> directory to the <code>/wp-content/plugins/</code> directory</li>
<li>Activate the plugin through the ‘Plugins’ menu in WordPress</li>
<li>Update the plugin settings</li>
<li>Set a Cron Job that will access the link https://domain.com/virtual-queue/maintenance/ where domain.com is your own domain name.</li>
<li>Go to Settings -> Permalinks / Permalink Settings and click Save Changes</li>
</ol>

Virtual Queue

By using this plugin you'll be able to allow only a specific number of visitors to navigate through your website.

queuefair

Queue-Fair, the original patented online queue for busy websites, is the <a href="https://www.g2.com/categories/virtual-waiting-room?tab=highest_rated" rel="nofollow ugc">top rated Virtual Waiting Room in the world</a>, according to review site G2.
When your site has more visitors than it can handle gracefully, the excess visitors are automatically sent away from your webservers to a branded online queue – it then sends visitors back to your site in first-come, first-served order at the rate that you desire, protecting your WordPress from web crashes due to high demand.
Our retail clients report that visitors who have seen a Queue Page add around 20% more to their shopping baskets.
You can get a free Queue-Fair Virtual Waiting Room for your WordPress with this plugin and a Queue-Fair Free Tier account from <a href="https://queue-fair.com/sign-up" rel="nofollow ugc">Queue-Fair.com</a>.
We queue hundreds of thousands of people every day.
By using the world’s most accurate, highest quality, most powerful and best value Virtual Waiting Room platform, you ensure that your site can keep selling at its optimum transaction rate. Your site visitors, shoppers, ticket buyers, and app users always get the responsive experience they require, even when you are really busy. They won’t see a crashed site.
More Orders 
Even the world’s biggest companies get overwhelmed by peaks in demand, particularly sudden peaks. All webservers have limits, and when they are exceeded, your visitors experience a crashed site. Queue-Fair stops traffic peaks from crashing your site.
More Customers 
Queue-Fair means you can serve new customers even when your servers are too busy to handle them. People who see an error page or no response at all from your site are unlikely to return – but you can reach all these people with Queue-Fair.
More Reliable 
Use Queue-Fair for timed events and onsales, as well as 24 hour always-on SafeGuard protection from unexpected peaks.
More Secure 
This plugin gives you our Server-Side Adapter, adapted for WordPress, for secure and unskippable queues when things get busy on your site..
You will need to create a Free Tier account at <a href="https://queue-fair.com/sign-up" rel="nofollow ugc">Queue-Fair.com</a> – we can upgrade you to Unlimited Service if you are running a larger/busier site.
<h3>External services</h3>
This Adapter runs in SAFE mode by default, which means it will connect to the Queue-Fair servers (at youraccount.queue-fair.net) on the first visit from each new visitor to a page that matches the Activation Rules that you set in the Queue-Fair portal, in order to check if the visitor needs to join a queue. The information sent is the visitor’s browser’s user agent, and the visitor’s IP address. It is possible to have the Adapter run in SIMPLE mode instead, which does not make this call – if that is required for your use-case please contact Queue-Fair support for assistance.
The Adapter will also download your queue settings, including the Activation Rules for your queues, once every 5 minutes from files.queue-fair.net, as is usual for all our server-side Adapters. No visitor information is sent on a settings download request. The downloaded settings file is cached in uploads/queue-fair-virtual-waiting-room/, the WordPress-recommended location for this kind of file.
For further details see <a href="https://github.com/queue-fair/php" rel="nofollow ugc">Our PHP Adapter Github repository</a>, the Technical Guide in the Help section of the <a href="https://portal.queue-fair.net" rel="nofollow ugc">Queue-Fair Portal</a>, or the <a href="https://queue-fair.com/developers" rel="nofollow ugc">Queue-Fair Developers Page</a>.
The Queue-Fair Virtual Waiting Room service is provided by Orderly Telecoms Ltd <a href="https://queue-fair.com/free-tier-terms-and-conditions" rel="nofollow ugc">Terms of use</a> <a href="https://queue-fair.com/privacy" rel="nofollow ugc">Privacy Policy</a>

Queue-Fair FREE Virtual Waiting Room

Stop Your Website Crashing - for Free! Manage traffic peaks gracefully. Treat your visitors with fairness with the top-rated Virtual Waiting Room.

Virtual Queue vs Queue-Fair FREE Virtual Waiting Room