This tutorial uses @upstash/redis which is designed for serverless runtimes for efficient connection handling. You can use your favorite Redis client, but you may have to deal with connection issues as described here.

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Database Setup

Create a Redis database using Upstash Console or Upstash CLI. Select the GCP US-Central-1 as the region. Copy the UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN for the next steps.

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Project Setup

Create a folder for your project, run npm init inside. Then install Upstash client with: npm install @upstash/redis

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The Code

Update index.js as below: 
const { Redis } = require("@upstash/redis/with-fetch");

const redis = new Redis({
  url: "UPSTASH_REDIS_REST_URL",
  token: "UPSTASH_REDIS_REST_TOKEN",
});

exports.helloCounter = async (req, res) => {
  let count = await redis.incr("counter");
  res.send("Page view:" + count);
};

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Run and Deploy

Deploy your function to Google Cloud with: 
gcloud functions deploy helloCounter \
--runtime nodejs16 --trigger-http --allow-unauthenticated
You will see the URL of your Cloud Function. Click to the URL to check if it is working properly. 
httpsTrigger:
  securityLevel: SECURE_OPTIONAL
  url: https://us-central1-functions-317005.cloudfunctions.net/helloCounter
In case of an issue, you can check the logs of your Cloud Function in the GCP console as below.