Filter query by result of other federated service

Hello! Thanks for any pointers/recommendations up front - I am trying to add filters to my federated graphql api (which has been super fun to learn about so far).

There are two services behind a gateway - the Accounts service and the Users service.

Within the Users service, I extend the Account type to add a list of users to each account, that way I can query for accounts and get a list of users. I want to be able to query the accounts service for accounts that have > 0 users, but can not figure out how to do this.

// Users Type Defs
  type User @key(fields: "_id") @key(fields: "account") {
    _id: ID!
    first_name: String
    last_name: String
    phone: String
    address: Address
    email: String!
    created_by: User
    stripe_customer_id: String
    stripe_connected_account_id: String
    profile_img: ID
    createdAt: Date!
    updatedAt: Date!
    account: Account!
  }

  extend type Account @key(fields: "_id") {
    _id: ID! @external
    users(getUsersInput: GetUsersInput!): GetUsersResponse!
      @requires(fields: "_id")
  }

And accounts –

//Accounts Typedefs
  type Account @key(fields: "_id") {
    _id: ID!
    email: String!
    password: String
    role: Int!
    activation: Activation
    createdAt: Date!
    updatedAt: Date!
  }
// Users Resolver - resolving Account.users
// Basically this is just a Model.find() method from mongoose wrapped in a function that allows
// pagination and filtering

export const Account: AccountResolvers = {
  users: async (account, args) => {
    try {
      const { filters, options } = GenerateMongoFilter({
        fieldFilters: args.getUsersInput,
        config: {
          operator: "AND",
          pagination: args.getUsersInput.config?.pagination,
        },
        fieldRules: [
          {
            location: "account",
            fieldFilter: {
              string: account._id,
              filterBy: "OBJECTID",
            },
            disabled: false,
          },
        ],
      });

      const users = await FindWithPagination({
        options,
        filters: filters,
        model: Users,
      });

      return users;
    } catch (error) {
      console.log(error);
      throw error;
    }
  },
};

Right now I can query the accounts service and get a list of accounts but if they have no users, it returns an empty array for the users property. Any idea how I can query accounts with a variable to say “hey I only want the account returned if it has users?”

Thanks! Let me know if you need to see anything else!