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furkantasel February 2016

How much overhead would a DNS call add to the response time of my API?

I am working on a cross-platform application that runs on iOS, Android and the web. Currently there is an API server which interacts with all the clients. Each request to the API is made through the ip (eg. This disallows me to move the backend quickly whenever I want to another cloud VPS as I need to update iOS and Android versions of the app with a painful migration process.

I though the solution would be introducing a subdomain. (eg http://api.example.com/customers). How much would an additional DNS call would affect the response times?


Michael B February 2016

The thing to remember about DNS queries is that, as long as you have configured your DNS sensibly, clients will only ever make a single call the first time communication is needed.

A dns query will typically involve three queries, one to the root server, one to the .com (etc) server, and a final one to the example.com domain. Each of these will take milliseconds and will be performed once, probably every hour or so whenever the TTL expires.

The TL;DR is basically that it is a no brainer, you get far far more advantages from using a domain name than you will ever get from an IP Address. The time is minimal, the packet size is tiny.

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Asked in February 2016
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