eligibility.js

const _ = require('underscore');
const { query, model, operation } = offer.eligibility;

// the query is parsed because the query string in
// the offer document is an undercore string template where
// the variables can be replaced with the provided value
const parsedQuery = JSON.parse(
  _.template(query)({
    brokeruserId: event.data.brokeruserId,
  })
);
// this gives us a parsed JSON query which can be further
// passed on to the mongoose model for querying

// models is an Object which contains the map of
// the collection name to mongoose model of that collection
const result = await models[model][operation](parsedQuery).exec();

if (result === expectedResult) {
  // do the needful
} else {
  // skip everything
}