Atlas 1,815 is MongoDB 1,815 's own hosted service, and its M0 tier costs nothing with no card on file. That makes it the practical way to give a deployed application a database and to try MongoDB Search and Vector Search, which Community Edition cannot run.
Creating one takes five steps: sign up, choose M0 with a region near your users, add a database user, add your IP to the access list, copy the connection string. The access list is the trap: it defaults to your address at signup, so the cluster stops answering the moment your connection gets a new one.
| Limit | M0 value |
|---|---|
| Storage / connections / ops | 0.5 GB, 500, 100 per second |
| Databases / collections | 100 / 500 |
| Data transfer | 10 GB each way per 7 days |
| Replica set | 3 nodes, MongoDB 8.0 |
| Backups, sharding, endpoints | not available |
The replica set row is the interesting one. A free cluster is a genuine three-node replica set, so multi-document transactions and change streams — both unavailable on the standalone mongod of Local Install — work on M0. The ops ceiling is enforced by throttling rather than errors, and a free cluster pauses after 30 days with no connections; resuming takes a minute and loses nothing.
What you give up is everything operational: no automated backups (use mongodump, Compass and Tools), no Performance Advisor, no rolling index builds, no failover testing. M0 also blocks server-side JavaScript.