# Package io.vertx.core.spi

- Interface Summary
  Interface | Description
  --- | ---
  ExecutorServiceFactory | The interface for a factory used to obtain an external `ExecutorService`.
  FileResolverFactory | A factory for the pluggable file resolver SPI.
  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.