An admin rest call to couchbase increases the Ops Per Second up to 4k and 5k

as you can see in the pic, whenever I want to find a document through Sync Gateway public and Admin Rest API, the statistics shows a heavy operation and involves the Couchbase badly, how can I do this in a normal form? it is only for searching one document through rest APIs, but it works properly by couchbase lite in Android and iOS, I need the use of these Rest APIs for my React JS clients.
the clients are more than 200.000, and if all them call the Sync Gateway Rest APIs, as the test for 1 search shows, it will definitely fail. so I don’t know how to handle it ?
actually I want the react JS clients use Couchbase through Sync Gateway, by it’s Public API.
the other clients like Android and iOS use their own SDK and there’s no problem, but I think and as my test shows, the React JS clients are going to face problems and by calling REST APIs , the Couchbase will face node fail over.
anyone knows that
1- First, why the Couchbase node fails??? I think it must work properly, but it doesn’t
2- what is the other ways to communicate with Couchbase from React JS?
it is good to know which all items on couchbase cluster is aound 2.700 K and 930K per nodes (3 nodes are in a cluster)