MIght be. Although since modern inboxes use real time websockets (or other technologies like server-push events) to handlle concurrent real-time messaging, updating the database shouldn't cause issues with receiving the messages as they are sent (although retrieving the chats on reload can be an issue if that's the case).
Anyways, the trouble was well worth it. Finally, Fiverr is using React for the front-end. Expect faster pageload speed, real-time effortless updates for various UI elements (like the dot on the notification bell and the number of messages for a chat) in real-time without the need of page reload. It's also gonna be much faster than the previous UI (considering how well React manages DOM manipulation with it's virtual DOM model), also expect future UI updates to be shipped faster (as React has state control built-in, is super modular and very developer friendly). I liked this decision of the tech team.