I have ported EchoPet to Mongo recently but in a way that removes mysql code. Are you interested to add native mongo support to the plugin? I can provide reference implementation.

I was talking about Mongo and he said I was welcome to submit a pr with mongo support. Never got around to it though.

Make sure any PRs go to the 3.x branch :)

Here's a patch I made for the main branch, it's working pretty good so far - https://gist.github.com/ninja-/e6d28e4d1350775bfade
I'll try to make one for branch 3.x