Nice blog! I also recommend to update index.js to avoid duplicate subscription that Gabriel E mentioned too. // Subscribe to creation of message const subscription = API.graphql( graphqlOperation(onCreateMessage) ).subscribe({ next: ({ provider, value }) => { setStateMessages((stateMessages) => [ ...stateMessages, value.data.onCreateMessage, ]); }, error: (error) => console.warn(error), }); return () => subscription.unsubscribe() }, []);