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]
----
Pool pool = MySQLBuilder.pool()
  .with(new PoolOptions().setMaxSize(maxSize))
  .connectingTo(database)
  .using(vertx)
  .build();
vertx.deployVerticle(() -> new VerticleBase() {
  @Override
  public Future<?> start() throws Exception {
    // Use the pool
    return super.start();
  }
}, new DeploymentOptions().setInstances(4));
----

You can also create a shared pool in each verticle:

[source,java]
----
vertx.deployVerticle(() -> new VerticleBase() {
  Pool pool;
  @Override
  public Future<?> start() throws Exception {
    // 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 = MySQLBuilder.pool()
      .with(new PoolOptions()
        .setMaxSize(maxSize)
        .setShared(true)
        .setName("my-pool"))
      .using(vertx)
      .build();
    return super.start();
  }
}, 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]
----
Pool pool = MySQLBuilder.pool()
  .with(new PoolOptions()
    .setMaxSize(maxSize)
    .setShared(true)
    .setName("my-pool")
    .setEventLoopSize(4))
  .using(vertx)
  .build();
----