You can set this up in control panel, While configuring an event, you'll notice an option to enable Reserve Tickets.
When enabled, tickets will be reserved for up to 5 minutes to allow the member to purchase the ticket before it's snapped up by another member. So as soon as they add it to their cart, we'll remove it from availability and then reserve it for 5 minutes.
Your member will see a banner stating the remaining time we'll reserve this for.
Meanwhile, your other members will see a Sold Out flag if the last tickets are being reserved.
If a member selects "Make a Change" or the 10 minutes runs out, the system will automatically return the tickets to inventory.