title: MySQL - Persistent connection vs connection pooling
body: <p>In order to avoid the overhead of establishing a new connection each time a query needs fired against MySQL, there are two options available:</p>
  
  <ol>
  <li>Persistent connections, whereby a new connection is requested a check is made to see if an 'identical' connection is already open and if so use it. </li>
  <li>Connection pooling, whereby the client maintains a pool of connections, so that each thread that needs to use a connection will check out one from the pool and return it back to the pool when done. </li>
  </ol>
  
  <p>So, if I have a multi-threaded server application expected to handle thousands of requests per second, and each thread needs to fire a query against the database, then what is a better option? </p>
  
  <p>From my understanding, With persistent connections, all the threads in my application will try and use the same persistent connection to the database because they all are using identical connections. So it is one connection shared across multiple application threads - as a result the requests will block on the database side soon. </p>
  
  <p>If I use a connection pooling mechanism, I will have all application threads share a pool of connections. So there is less possibility of a blocking request. However, with connection pooling, should an application thread wait to acquire a connection from the pool or should it send a request on the connections in the pool anyway in a round-robin manner, and let the queuing if any, happen on the database? </p>