DocumentDB Parity

The LocalStack DocumentDB Docs describe that they run MongoDB under the hood and therefore may not have exact parity with DocumentDB.

Does this mean it is the exact same as MongoDB, and there is no effort to match DocumentDB API in any capacity? Even in Pro version of Localstack?


Hi — Thanks for reaching out.

Its not the “same” as MongoDB, since we have extensive parity testing against AWS, which involves our Internal & External Test Suite, Terraform validation, and snapshot testing.

You can checkout the coverage right here on DocumentDB’s API coverage page — DocumentDB | Docs

I hope this helps!

Hi HarshCasper,

Thank you for your support. I see the tests described on that page and I see many of them mentioning Aurora and Postgres. I do not understand the point of these being listed on the DocumentDB page, however I am new to the localstack ecosystem.

The tests seem to be evaluating AWS Infrastructure operations for DocumentDB, however I am looking to understand the API parity between DocumentDB server running in Localstack locally, and the DocumentDB server running in AWS.

For example,

If I run a query against localstack DocumentDB cluster, will it successfully fail if I use an unsupported operator such as $expr?

I am trying to understand if the Localstack DocumentDB implementation will be a good tool to ensure application code is compliant with the real DocumentDB server.

Thank you for the consideration.

Hi @pritchardtw,

This difference is already mentioned in our documentation DocumentDB (DocDB) | Docs (

Because LocalStack utilizes a MongoDB container to provide DocumentDB storage, LocalStack may not have exact feature parity with Amazon DocumentDB. The database engine may support additional features that Amazon DocumentDB does not and vice versa.

You can find more differences on the AWS documentation pages:
Functional Differences: Amazon DocumentDB and MongoDB - Amazon DocumentDB
Supported MongoDB APIs, Operations, and Data Types - Amazon DocumentDB

Hi @Marcel ,

Thank you for the consideration. My interpretation of the documentation was that there may be discrepancies in the database engine leading me to believe there was possibly some effort put in place to match the document DB database engine, however you have been able to confirm with me that is not the case. We should not expect things that work in localstack DocumentDB database to mean they should also work in aws DocumentDB database without first consulting the compatibility guidelines put forth by AWS. We will take this into consideration for our localstack evaluation.


Hi @pritchardtw,

If you encounter any issues or ambiguities between the AWS DocDB and LocalStack offerings, please let us know in Feature Requests, so we can deliver a fully functional product to you.

Thank you,