The /oauth2/revoke endpoint throws {"__type":"UnknownOperationException"}

The data payload should be URL-encoded, not JSON. You can use the querystring module to encode your data:

var axios = require("axios").default;
var querystring = require('querystring');

var data = querystring.stringify({
    client_id: '{yourClientId}',
    token: '{yourRefreshToken}',
    token_type_hint: 'refresh_token' // Optional, but recommended
});

var options = {
    method: 'POST',
    url: 'https://{yourDomain}/oauth2/revoke',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    data: data
};

axios.request(options).then(function (response) {
    console.log(response.data);
}).catch(function (error) {
    console.error(error);
});

Key Source:

• Revoke endpoint

Hi,

The request content type is not correct, you must use application/x-www-form-urlencoded instead of application/json.

Take a look at the following example from the AWS documentation:

  POST /oauth2/revoke HTTP/1.1
        Host: https://mydomain.auth.us-east-1.amazoncognito.com
        Accept: application/json
        Content-Type: application/x-www-form-urlencoded
        token=2YotnFZFEjr1zCsicMWpAA&
        client_id=djc98u3jiedmi283eu928