+6 votes
In that case, is there a threshold after which you start to experience those issues? Does this happen with any mediation platform in particular? Or with all of them?
by (890 points)

3 Answers

+2 votes
In my experience, yes. But depends on the game/app: for placements that shows up from time to time it is not a big deal (like a random rewarded video). On the other hand, if your game/app constantly loads a new Ad right after the previous one, or if you need a quick load right after the application came from background, it could be an issue.
by (500 points)
+1 vote
No serious latency should occur, even with 20 instances.

On a different note, I'm not sure 20 instances are needed for a single ad location. If you didn't maximize 99% of impressions after 10, you are probably using the wrong ad networks.
by (680 points)
I don't necessarily agree with this, I understand the principle but if you have 25 instances with fixed eCPM floors with 6 ad networks , it's all about the availability rate of each instance.

Then it's normal that some instances will provide very low fill at certain eCPM, in that case you can either reduce the floor or deactivate that instance.

The bottom line here, in my opinion, is that more instances are set, more chances there are to get a higher eCPM.
Second this. In my experience, I haven't seen significant latency with 20+ instances.
Having 3-6 instances in your waterfall per ad network will create a healthy competition between your ad networks (including any ad networks in bidding), and give you an indication of network performance. Over time, if you see very few impressions on some of the instances, I would disable them.
+1 vote

This article by Vincent Fevrier from MoPub is pretty useful. https://www.mopub.com/en/blog/top-14-waterfall-best-practices-and-recommendations

Among all of the useful recommendations, here is an answer to your question:

We found that for Tier 1 countries with high eCPM average, an interstitial waterfall should have between 40 to 70 calls. For rewarded video, between 30 to 60 calls and for Banner between 15 to 30 calls. For lower eCPM country tiers, try to shorten your waterfall.

I can agress with this, as most waterfall I manage have this amount of calls as well. As you can see, it is much higher than your initial assumption of a loss of revenue above 20 instances :)

You should of course try different configurations and measure whether they are causing latency. Depending on your volume of DAU and impressions, but also on the type of app you have, a configuration with less instances can also lead to a better ARPDAU. You need to experiment !

by (210 points)
Thank you for your feedback, trust me since I posted the question I experimented a lot! ;)
But also, with more and more bidders fortunately waterfalls are shrinking a bit, then we keep going granular if it makes sense (aka: instances bring an impact and they have enough share of voice so maintaining them operationally it's cost/opportunity positive)