MongoDB Atlas offers a free tier that allows users to explore their app ideas without incurring costs, with features such as MongoDB Atlas Search, Collections view, and Aggregation Pipeline Builder available on both paid and free clusters. The free tier is deployed on the latest version of MongoDB, providing users with on-demand materialized views, client side FLE, and wildcard indexes, among other benefits. It is also distributed across multiple cloud providers, including AWS, GCP, and Azure, making it accessible to users in various regions. Users can spin up a free tier cluster per project, test out new features, or use it as a development environment without any cost implications.