I was looking at a client's website today and noticed something that would help it load faster. This client manages DNS and their hosting themselves. If we were managing it, I would have just taken care of it without bothering her.
Here's an excerpt of the email I wrote (domain name and IP address changed):
I was looking at your website today and noticed something in your DNS that should get fixed:
yourdomain.com. 141 IN A 188.8.131.52
www.yourdomain.com. 3599 IN A 184.108.40.206
This probably doesn't mean much to you, so I'll explain it...
Above, there are actually two separate domains - your domain and then the "www" subdomain. People are used to typing in either, so the general practice is to have both of them point to your website. This part is fine.
Next, there are two numbers:
This is called the "time to live" (TTL) and it's in seconds. This is how long your DNS record is good for. Both of these values are way too low. What you want is for your domain name (either one) to resolve to an IP address quickly. The way this is set up, people have to wait a long time since they'll first go to their ISP's DNS and there they will find that your DNS record already expired since it's only good for either 2 min and 21 seconds or else 60 hours.
The one for 141 seconds is just WAY too low. If someone spends 5 minutes on your website and clicks from page to page, they're going to have to do a couple lookups just in that one session alone.
The "www" one for 60 hours is probably ok but I would set it higher to speed up the load time.
The reason this can change is if you plan on moving your hosting. In that situation, you would want to go in a few days beforehand and set it lower. If you're not planning on doing that, there's no reason to have it set so low because it's only slowing down access to your website. Please ask your DNS host to increase this. I like 86400 seconds, which is 1 day.
If they're doing that for you, they might also want to change "www.yourdomain.com" to be a "CNAME" record instead of an "A" record. That's the best practice there.
Did that make sense?
If your DNS is set up properly already, you actually won't be able to take advantage of this but I've seen a lot of websites/domains set up incorrectly, so there's a good chance that you could make this change and see your website load more quickly.
Really, it comes down to the user experience. We like to say "think like Google" for things like this - and basically everything. What this really means is to provide the best user experience because that's what Google is trying to do. If two websites are theoretically equal with all aspects of Google's algorithm but one has their DNS set so that it loads more quickly, that website's going to get the advantage and rank higher. It's a result Google will want to send people to.
It's not only DNS that you have to think about - it's many things:
Technical things like this make a difference in your rankings. If your website was developed by someone and they didn't look over each and every technical aspect of your website, you could be losing rankings to your competitors who had their website set up right with optimization.