I was quite happy with armzilla/amazon-echo-ha-bridge, but startup on my raspberry pi took more than four minutes, so I wondered if I could speed it up by replacing the ElasticSearch backend with hibernate and an embedded database like H2.
Long storry short, I only gained about 10s, so in the end I don't consider it worth the effort. Still, if you run a little database daemon anyway, you might have bigger benefits, so I don't delete this fork.
But it is certainly more proof-of-concept than fit-for-production.