# Package io.vertx.core.spi

- Interface Summary
  Interface | Description
  --- | ---
  ExecutorServiceFactory | The interface for a factory used to obtain an external `ExecutorService`.
  JsonFactory | A factory for the plug-able json SPI.
  VerticleFactory | Has responsibility for creating verticle instances.
  VertxMetricsFactory | A factory for the plugable metrics SPI.
  VertxServiceProvider | Entry point for loading Vert.x SPI implementations.
  VertxThreadFactory |
  VertxTracerFactory | A factory for the plug-able tracing SPI.

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