Your website is a monster where is very difficult to get the useful information. I wanted to use Realm to use a mongo cluster and after hours trying I give up. I couldn't connect to the cluster after I created serveral ids (app, api, another api id, ...) Solution: Let's say I have a single cluster and a single realm app created. Just give me the code with all the ids necessary. In my case I wanted to run it from the browser. This is the code I tried to execute: const app = new Realm.App({ id: 'tradeapp-bozmd' }); const credentials = Realm.Credentials.apiKey('51f080c1-f0f7-41de-a69c-9a408db76e57'); // Authenticate the user const user = await app.logIn(credentials); // `App.currentUser` updates to match the logged in user console.assert(user.id === app.currentUser.id); this.db = user.mongoClient('mongodb-atlas').db('TradeTeam'); console.log("this.db :", this.db ) One of the issues was that I couldn't find anything about Realm inside cloud.mongodb.com. I had to search on internet (gpt told me about Realm). Terrible. Simplify your website. What a terrible design.