In kdb, GET requests are normally mapped to .z.ph[1] which synchronously returns the HTTP response. dash supports this as well (sync mode) when it doesn&#x27;t understand the query string parameters, and then dash works just like a faster .z.ph for KDB.<p>Async mode is designed when dash knows what the HTTP response <i>will be</i> and can send it immediately. It then relies on kernel queueing to send the same message to kdb which allows for logging (or other processing, like HLL or anything else). This gives a significant performance boost so it&#x27;s worth optimising.<p>[1]: <a href="http:&#x2F;&#x2F;code.kx.com&#x2F;wiki&#x2F;Reference&#x2F;dotzdotph" rel="nofollow">http:&#x2F;&#x2F;code.kx.com&#x2F;wiki&#x2F;Reference&#x2F;dotzdotph</a>