MongoDB is a relational database management system (RDBMS) replacement for web applications. So, when we have something close to RDBMS, MongoDB could be of good use.
It gives us the additional partition tolerance, which RDMBS doesn’t offer, but it has problems with availability. Nonetheless, if we want more scalability, MongoDB would be the right choice for us. It’s suitable for real-time analytics and high-speed logging, and it’s highly scalable as well. Craigslist uses MongoDB for archived posts.