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To summarize, the blog Use-Cases are:

1. Imagine that you need to connect to resources like Database Clients or Feature Flag Clients where you create a connection every time -- Seems simple --Yah!!!-- but in FaaS we need to think on a major scale.
2. Imagine that this same code runs for 1,000,000 users, per second - What would happen then !!!
3. The golden rule - take advantage of the global state of your Lambdas and initialize your connections once

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Imagine that you need to connect to resources like Database Clients or Feature Flag Clients where you create a connection every time. You create a code that will look like this:

const mysql = require('mysql')

module.exports.myhandler = function (event, context, cb) {
  const conn = mysql.createConnection({
    // mysql connection info
  });

  conn.query("SELECT * FROM items", (error, results) => {
    if (error) {
      cb(error, null)
    } else {
      cb(null, results)
    }
  })
}

You can see that every time this function is executed, it will connect to a MySQL DB and then query something for us. Seems straightforward and looks like there’s no problem, but in FaaS we need to think on a major scale.

Imagine that this same code runs for 1,000,000 users, per second. This will absolutely crash our MySQL DB since we create a DB connection per user.

To solve this problem, thankfully, AWS Lambda provides a global state that will be executed just once and keep the state while the Lambda is alive.

• For DB connections, we can create a connection pool and
• re-use that same connection for all the concurrent Lambdas.

Our code should now look like:

module.exports.myhandler = function (event, context, cb) {
  conn.query("SELECT * FROM items", (error, results) => {
    if (error) {
      cb(error, null)
    } else {
      cb(null, results)
    }
  })
}

The golden rule is, take advantage of the global state of your Lambdas and initialize your connections once.