Error PROTOCOL_CONNECTION_LOST

I am using Connection Pooling with the following options -

const options = {
    connectionLimit: config.connection_pool,
    host: mysqlHost,
    user: mysqlUser,
    password: mysqlPassword,
    database: mysqlDb,
    multipleStatements: true,
    Promise: bluebird,
};

The wait_timeout configuration of MySQL on the server is 5 seconds. It used to be 10 seconds before I changed it to 5. Since then, I have been observing query failures all over my logs. All of them throw the same error.

The connection config is a bit confusing since it does not provide any related config.
I came across two related parameters - connectTimeout and acquireTimeout

The default value of connectTimeout is 10 seconds. This creates some confusion in my mind. Has this anything to do with the connections timing out ?

When does a pool truly end a connection? When does the pool get to know that the connection has been closed from the MySQL server's end?

I use pool.query in the program and this creates a problem in using error handlers and solving the issue on a global scale.

Any help would be much appreciated.

Start with the pool.query usage and connection options shown in the issue. Investigate how MySQL wait_timeout relates to connectTimeout, acquireTimeout, and PROTOCOL_CONNECTION_LOST, and document when the pool detects connections closed by the server.