MongoDB

MongoDB is based in New York. Developers store JSON-like documents, use its query language and drivers, and increasingly run that workload on Atlas rather than on servers they operate.

In 2018 the company moved MongoDB Server from an open-source license to the Server Side Public License. A cloud provider that wants to sell the server as a service has to open-source its own management stack or take a commercial license, which is why Amazon DocumentDB, Azure Cosmos DB, and others built compatible or alternative APIs instead of hosting unmodified MongoDB.

Applications written to MongoDB drivers, indexes, and aggregation pipelines do not move to PostgreSQL without a rewrite. That switching cost sits with the customer whether they run Atlas, self-host, or try a cloud vendor's partial compatible service.

The Server Side Public License is what keeps hyperscalers from reselling the official server as their own managed product.

Atlas is MongoDB's answer, a first-party cloud where the company captures the management fee.

Driver-level compatibility claims from cloud rivals still leave gaps in aggregation, transactions, and tooling.

A development team with years of MongoDB queries treats a database change as an application rewrite.

Companies that outgrew self-hosted clusters are pushed toward Atlas because the public clouds do not sell official MongoDB.