### Step 1: import `FastAPI` { #step-1-import-fastapi }

{* ../../docs_src/first_steps/tutorial001_py39.py hl[1] *}

`FastAPI` is a Python class that provides all the functionality for your API.

/// note | Technical Details

`FastAPI` is a class that inherits directly from `Starlette`.

You can use all the <a href="https://www.starlette.dev/" class="external-link" target="_blank">Starlette</a> functionality with `FastAPI` too.

#### Detalles Técnicos de `lru_cache` { #lru-cache-technical-details }

`@lru_cache` modifica la función que decora para devolver el mismo valor que se devolvió la primera vez, en lugar de calcularlo nuevamente, ejecutando el código de la función cada vez.

            // otherwise you end up with a wrong server name for kerberos
            // seems to be correct according to
            // https://lists.samba.org/archive/samba-technical/2009-August/066486.html
            // UniAddress addr = UniAddress.getByName(authDomain, true, tf);
            // SmbTransport trans = tf.getTransportPool().getSmbTransport(tf, addr, 0);

We are doing it here to demonstrate how **FastAPI** handles scopes declared at different levels.

///

{* ../../docs_src/security/tutorial005_an_py310.py hl[5,141,172] *}

/// info | Technical Details

`Security` is actually a subclass of `Depends`, and it has just one extra parameter that we'll see later.

**Technical Details**: If you want to know more of the technical details you can check out the PR description [#4575](https://github.com/tiangolo/fastapi/pull/4575).

### Internal

net.cy
org.cy
press.cy
pro.cy
tm.cy

// cz : https://www.iana.org/domains/root/db/cz.html
cz

// de : https://www.iana.org/domains/root/db/de.html
// Confirmed by registry <******@****.***> (with technical
// reservations) 2008-07-01
de

// dj : https://www.iana.org/domains/root/db/dj.html
dj

// dk : https://www.iana.org/domains/root/db/dk.html
// Confirmed by registry <******@****.***> 2008-06-17

  }

  @CanIgnoreReturnValue
  public MapMaker concurrencyLevel(int concurrencyLevel) {
    checkArgument(
        concurrencyLevel >= 1, "concurrency level (%s) must be at least 1", concurrencyLevel);
    // GWT technically only supports concurrencyLevel == 1, but we silently
    // ignore other positive values.
    return this;
  }

  public <K, V> ConcurrentMap<K, V> makeMap() {
    return new ConcurrentHashMap<K, V>(initialCapacity);

   * Notifies the listener that a removal occurred at some point in the past.
   *
   * <p>This does not always signify that the key is now absent from the cache, as it may have
   * already been re-added.
   */
  // Technically should accept RemovalNotification<? extends K, ? extends V>, but because
  // RemovalNotification is guaranteed covariant, let's make users' lives simpler.
  void onRemoval(RemovalNotification<K, V> notification);

alguns dos principais conceitos que você provavelmente deve ter em mente ao implantar uma aplicação **FastAPI** (embora a maior parte se aplique a qualquer outro tipo de aplicação web).

Você verá mais detalhes para ter em mente e algumas das técnicas para fazer isso nas próximas seções. ✨...

de los conceptos principales que probablemente deberías tener en cuenta al desplegar una aplicación **FastAPI** (aunque la mayoría se aplica a cualquier otro tipo de aplicación web).

Verás más detalles a tener en cuenta y algunas de las técnicas para hacerlo en las siguientes secciones. ✨...