dcdevfest: this was a great conference right in the midatlanti area in the capital one hq. was really a good crowd interested in a bunch of deep tech talks. nice facilities, not much in the way of vendor space.
aws reinvent - really always enjoy this because it's really the big event of the year. everyone who's involved in technology/cloud/whatever shows up to learn, pitch and hang out. there's some feelings of traditional "trade show" buy there's value in the whole experience. vegas is a bit much.
mongodb world - a good event if you are specific to this market. workshops are helpful.
At MongoDB World this past week they did a demo of stitch where they actually built something similar with no back end code required and used the Clarifai API and an angular front end. It took like less than 80 minutes and could like run on prod of I wanted.