No, but you are concerned about scalability while I don't know what you are doing, that is the key word that I would use a 3rd party api. Lowest overhead and easiest to be scaling with.
"Scalability" is ultimately limited by the Bitcoin network, which-- by definition-- a Bitcoin full node can handle. Interposing a 3rd party does not necessarily improve scalability-- it likely reduces it, especially since you're talking about unpaid services, so there is nothing to fund your utilization-- and using a third party service necessarily reduces security, more so than SPV, and necessarily adds additional points of failure: the reliability of third party blockchain services has been very low.
I'm sad to see that no one seems to have noticed the Baron link I gave above. It's a full order processing solution based on a local full node. It deserves more attention.
Your right in one aspect and you are wrong in another aspect. Scalability is not ultimately limited by the bitcoin network, but also by connections/users. Bitcoin-core I think is becoming less and less used by companies just because it is so heavy and not scalable. It really tops out at only a few 1000 connections, even raising the file limit from 1024 (default for most linux systems) to higher and higher numbers doesn't help anymore. Then you probably need to run a bitcoin proxy as I have been using, that manages connections and limits. This causes another problem which we have seen time and time again, that if you do a withdraw and don't say it could take 12-24 hours to process, and it doesn't show up on the network in a few seconds. The idea that company is now a scammer, is what consumes the mind. So now you are not able to use the the programical instant withdraw that only the bitcoin network as a bootstrap startup without risking your reputation.
I believe we are failing as a community in many ways about this, I recommend 3rd party apis because that is the only solution currently. There are no other full nodes that can handle this unless you enter the enterprise stage. I don't think anyone wants to do that unless they have to. I think as btcd, tosh.io, and bitcoin-core grow we will see many forks addressing this problem. Until then there is really no way to be trustless and scale.