- Scaling is not infinite, it's up to 20gb per partition key (1), which can't be changed after document creation.
- One set of global indices, no equivalent to DynamoDB's secondary indices.
- Still can't run their docker container on mac (2) natively.
- Weird SQL-like dialect that's required for all but the simplest queries. JOINs are spectacularly awkward.
- Tooling is horrific. Based on the previous point, no existing tooling works for it (and nobody is building tooling for a DB with such minimal market share). For example, I needed to manually deleted 30 or so documents/rows yesterday - only way to achieve this is with 30 separate click-to-deletes in their UI.
- Minimises analytics options. There exist a plethora of business intelligence type tools that will happily sit on top of most common DBs. None of them like CosmosDB. So you're stuck with synapse link or whatever MS calls it now.
Overall it seems to combine the worst aspects of both RDS and document stores, with the worst aspects of both traditional and serverless infrastructure.
(1) https://learn.microsoft.com/en-us/azure/cosmos-db/partitioni... (2) https://learn.microsoft.com/en-us/azure/cosmos-db/local-emul...