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.