EPS just keeps track of a set of scriptPubKeys associated with the user's seed, correct? I am not necessarily looking for something lightweight, I need something that can answer a lot of queries about any scriptPubKey fast.
I mean stuff like this https://github.com/romanz/electrs/issues/79
Also, what exactly do you mean by "very bad at handling mempool transactions"? 
I've not had too many issues with it, but I'm not trying to do anything really extraordinary with electrs... basically just letting it run off of a standard Bitcoin Core node and connecting to it locally from my personal copy of Electrum...
I've not had too many issues with it, but I'm not trying to do anything really extraordinary with electrs... basically just letting it run off of a standard Bitcoin Core node and connecting to it locally from my personal copy of Electrum...I mean stuff like this https://github.com/romanz/electrs/issues/79