First API call is slow

I made on a shared OVH hosting an API with Symfony 7 for the backend. The frontend is under Angular 18.2 Everything works fine except for the first API call which is allways slowlier than the other.

I did the connector with Curl then i change for Guzzle, it has improved the response time but it is allways too slow. Initialy i did the Front with AngularJS 1.82, and so then i change to Angular 18.2 It does not improved performance but i can use modern tools like RXJS to improve API Calls.

Do you have any ideas for improving first call response time ?

Here is my adaptator code for the token creation and a simple GET Token

    public function generateCreatioToken() {
    $client = new Client();

    $options = [
        'form_params' => [
          'client_id' => $this->clientId,
          'client_secret' => $this->clientSecret,
          'grant_type' => 'client_credentials'
        ]];
    $request = new Request( 'POST', $this->oauthurl .'/connect/token', 
                            ['headers' => ['User-Agent' => null]]);
    $res = $client->sendAsync($request, $options)->wait();

    return json_decode($res->getBody());
}

Get

    /*
 * READ
 * Requête en GET sur CRM
 * $apiQuery: array dont le contenu des éléments est encodé en URL
 */
public function WSGETBPM($collection, $apiQuery, $token, $nbresult = 10000) {

    $client = new Client();
    $headers = [
      'Accept' => 'application/json; odata=verbose',
      'Authorization' => 'Bearer '.$token,
      'User-Agent' => null
    ];
    
    $targetUrl = $this->urlapi . '/0/ServiceModel/EntityDataService.svc/' . $collection;
    if (count($apiQuery) > 0) {
        $targetUrl .= '?' . implode('&', array_map(function ($item) {
            return $item[0] . '=' . $item[1];
        }, array_map(null, array_keys($apiQuery), $apiQuery)));
    }
    $request = new Request('GET', $targetUrl, $headers);
    $res = $client->sendAsync($request)->wait();
    return $res->getBody();
}

With Angular my service code:

  getOrderNumberById(orderId: string): Observable<OrderValidation> {
const options = { params: new HttpParams().set('orderId', orderId) };
return this.http.post<OrderValidation>(this.url + 'Creatio/getOrderNumberById', options).pipe(
  retry(3),
  catchError(this.handleError)
)

}

Using an interceptor:

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
const authToken = this.authService.getAuthToken();

const authReq = request.clone({
  setHeaders: {
    'Authorization': `${authToken}`,
    'Content-Type': 'application/json; charset=utf-8'
  }
})

On my API Adapter i added Guzzle Cache:

    $stack = HandlerStack::create();
    $stack->push(new CacheMiddleware(), 'cache');
    // Initialize the client with the handler option
    $client = new Client(['handler' => $stack]);

In the .htaccess:

<ifModule mod_headers.c>
    Header set Connection keep-alive
</ifModule>

And i added a planned task which make at least an API call per hour.

It looks good.