I use queueing as well for external api calls. For instance, I use mailgun to deliver emails, but I do not make the api call to mailgun during page execution. Mailgun calls are made via curl. Imagine what a traffic spike and curl use will do to the server. So to remedy the situation, I store the request in queue, and have another script via cron job pick up the requests and execute them one at a time. This helped improve performance dramatically when I get server traffic spikes.