Hi @Mat_Jung,
Glitch provides hosting for applications, but is not a general hosting/infrastructure provider where you can run additional services like databases. As mentioned, you can connect a Glitch application to a database cluster hosted elsewhere. You should make sure you have appropriate security configured (user authentication, TLS/SSL network encryption, firewall/whitelist) to limit access as much as possible. Limiting access via firewall or whitelist can be more difficult from shared hosting providers which can potentially have a large (and changing) range of originating IPs.
Your other topic on Relationship between Atlas, MongoDB, and Cluster Providers has some helpful context for cluster providers.
FYI: mLab was acquired by MongoDB in October 2018 and those users have now been migrated to MongoDB Atlas.
Regards,
Stennie