An example of how to make an external API call in WordPress and cache the response.

api-caching-example.php

<?php

$cache_key   = 'my_api_call_response';
$response = get_transient( $cache_key );
if ( ! $response ) {
  $response    = wp_remote_get('https://example.com/api/v1/endpoint');
  $status_code = (int) wp_remote_retrieve_response_code( $response );
  $body        = wp_remote_retrieve_body( $response );
  $data        = json_decode( $body, true );
  if ( 200 === $status_code && $data ) {
    // Process data
    set_transient( $cache_key, $response, HOUR_IN_SECONDS );
  }
}