You can share an pool between multiple verticles or instances of the same verticle. Such pool should be created outside
a verticle otherwise it will be closed when the verticle that created it is undeployed

[source,java]
----
MySQLPool pool = MySQLPool.pool(database, new PoolOptions().setMaxSize(maxSize));
vertx.deployVerticle(() -> new AbstractVerticle() {
  @Override
  public void start() throws Exception {
    // Use the pool
  }
}, new DeploymentOptions().setInstances(4));
----

You can also create a shared pool in each verticle:

[source,java]
----
vertx.deployVerticle(() -> new AbstractVerticle() {
  MySQLPool pool;
  @Override
  public void start() {
    // Get or create a shared pool
    // this actually creates a lease to the pool
    // when the verticle is undeployed, the lease will be released automaticaly
    pool = MySQLPool.pool(database, new PoolOptions()
      .setMaxSize(maxSize)
      .setShared(true)
      .setName("my-pool"));
  }
}, new DeploymentOptions().setInstances(4));
----

The first time a shared pool is created it will create the resources for the pool. Subsequent calls will reuse this pool and create
a lease to this pool. The resources are disposed after all leases have been closed.

By default, a pool reuses the current event-loop when it needs to create a TCP connection. The shared pool will
therefore randomly use event-loops of verticles using it.

You can assign a number of event loop a pool will use independently of the context using it

[source,java]
----
MySQLPool pool = MySQLPool.pool(database, new PoolOptions()
  .setMaxSize(maxSize)
  .setShared(true)
  .setName("my-pool")
  .setEventLoopSize(4));
----