How many sites can be served with 50,000 dns queries?

Some DNS services offer to host your DNS for free with a limit like '50,000 DNS queries a month'.

• Does each website visit trigger a lookup?
• What volume of traffic can be served with 50,000 requests per month?

Solution 1:

What is the time frame they are talking about? Second, Minute, Hour, Day, Month, Year?

Does each website visit trigger a lookup?

Yes and no. Every time someone hits your site a DNS lookup is necessary for them to get the IP to connect to. However, Due to caching at various levels of the DNS infrastructure your servers may or may not get a DNS request.

What kind of volume of traffic can be served with 50,000 requires?

It's kinda hard to say exactally. Here at Stack Exchange we get ~180 DNS req/s for a network that gets ~1-2MM visitors a day.

That works out to:
10,800 req/min
648,000 req/hour
15,552,000 req/day
108,864,000 req/week
435,456,000 req/month
5,225,472,000 req/year

Solution 2:

You need to ask what the time window for that 50k queries is and the TTL (time to live).

If it's a month then you could be in trouble as 50k lookups isn't that many even for a smallish site and don't forget you have zero control over this, I could sit here and force 50k lookups in minutes if I wanted to.

If it's per day and you have a 24hr or longer TTL then you may be ok, of course things like web trawlers will use some before you've even started.

If it's per hour or less then you should be fine.

So as you can see, it all depends on the timescale they're talking about, personally I'd avoid DNS providers offering such low numbers of queries, they're very light and even a small server can handle millions per minute, I think they're trying to gouge you.