what's the scrappy open source alternative nosql db that actually needs users/support/tutorials now that mongodb has gone IPO? https://www.cnbc.com/2017/10/19/mongodb-mdb-ipo-stock-price-on-first-trading-day.html (to be clear, I like mongodb and have friends that work there and would continue to suggest it to clients, but I'd rather spend my own time supporting smaller, more radical, less cash-rich projects)