Correct Usage of Global Variables

handler.js

let cachedData = {};


exports.handler = async (event) => {
    if (cachedData && cachedData.expiresOn > Date.now() ) {
         const response = {
            statusCode: 200,
            body: `The weather is ${cachedData.weather} and it is ${cachedData.temperature} decrees Celcius`,
        };
        return response;
    }
    
    const { weather, temperature } = await fakeWeatherAPIRequest(event);
    
    cachedData = {
        weather,
        temperature,
        expiresOn: Date.now() + 30 * 1000 
    };
    
    const response = {
        statusCode: 200,
        body: `The weather is ${weather} and it is ${temperature} decrees Celcius`
    };
    return response;
};


const fakeWeatherAPIRequest = async (event) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve({
                weather: 'sunny',
                temperature: '15'
            });
        }, 3000);
    });
};